emshack@chromium.org koretadaniel@chromium.org top-chrome-desktop-ui@google.com The type of Page Action currently shown. Logged once per ephemeral page action the first time it becomes visible on a given page. Tab switches will only trigger logging for any page actions that have not already been logged as visible on this page. yeroshkin@chromium.org top-chrome-desktop-ui@google.com The number of Page Action Suggestion Chips currently active. Measured each time a new suggestion chip is shown. yeroshkin@chromium.org top-chrome-desktop-ui@google.com The type of Page Action suggestion chip that was shown in a collapsed state (icon only) due to insufficient space in the omnibox. Logged once when the chip is originally shown. yeroshkin@chromium.org top-chrome-desktop-ui@google.com The preferred width of the Page Action suggestion chip that was shown in a collapsed state due to insufficient space in the omnibox. Logged once when the chip is originally shown. yeroshkin@chromium.org top-chrome-desktop-ui@google.com The type of Page Action suggestion chip that was shown. Logged once when the chip is originally shown, regardless of whether it was collapsed or expanded. Used as a denominator for CollapsedDueToSpace.ActionType to calculate the collapse rate. emshack@chromium.org koretadaniel@chromium.org top-chrome-desktop-ui@google.com The type of Page Action currently shown as a chip. Logged once per ephemeral page action the first time it becomes visible on a given page. Tab switches will only trigger logging for any page actions that have not already been logged as visible on this page. emshack@chromium.org koretadaniel@chromium.org top-chrome-desktop-ui@google.com The number of ephemeral Page Actions currently shown. Measured each time a new page is loaded, and then again when each new page action appears on the same page. koretadaniel@chromium.org alsan@chromium.org top-chrome-desktop-ui@google.com The number of ephemeral Page Actions currently shown. Measured each time a new page is loaded, and then again when each new page action appears on the same page. This recorded only for the new page action framework. emshack@chromium.org top-chrome-desktop-ui@google.com Records events related to percentage of pages with actions calculation. The percentage of pages with at least one ephemeral action shown can be calculated by computing "Action Shown" / "Page Shown". The percentage of pages with multiple ephemeral actions shown can be calculated by computing "Multiple Actions Shown" / "Page Shown". "Page Shown" is logged once when a given page is first loaded, "Action Shown" is logged when the first page action is displayed on a given page, and "Multiple Actions Shown" is logged the first time a page action appears on a given page alongside a second page action. koretadaniel@chromium.org alsan@chromium.org top-chrome-desktop-ui@google.com Records events related to percentage of pages with actions calculation. The percentage of pages with at least one ephemeral action shown can be calculated by computing "Action Shown" / "Page Shown". The percentage of pages with multiple ephemeral actions shown can be calculated by computing "Multiple Actions Shown" / "Page Shown". "Page Shown" is logged once when a given page is first loaded, "Action Shown" is logged when the first page action is displayed on a given page, and "Multiple Actions Shown" is logged the first time a page action appears on a given page alongside a second page action. This recorded only for the new page action framework. koretadaniel@chromium.org top-chrome-desktop-ui@google.com Records whether the {PageActionType} page action was shown at least once during a navigation. Logged once per navigation when the user navigates away or the tab is closed. koretadaniel@chromium.org emshack@chromium.org top-chrome-desktop-ui@google.com Records events related to {PageActionType} page action click through rate (CTR) calculation. The CTR can be calculated by computing "Clicked" / "Shown". "Clicked" means the page action was clicked. "Shown" means that the page action was displayed. "Shown" is logged once per page action the first time it becomes visible on a given page, and "Clicked" is logged once per click. emshack@chromium.org koretadaniel@chromium.org top-chrome-desktop-ui@google.com Records events related to overall ephemeral page action click through rate (CTR) calculation. The CTR can be calculated by computing "Clicked" / "Shown". "Clicked" means the page action was clicked. "Shown" means that the page action was displayed. "Shown" is logged once per page action the first time it becomes visible on a given page, and "Clicked" is logged once per click. emshack@chromium.org koretadaniel@chromium.org top-chrome-desktop-ui@google.com The number of ephemeral Page Actions currently shown. Measured each time a page action is clicked. bmcquade@chromium.org hajimehoshi@chromium.org Counts the events related to the back-forward cache, like when the page is put into the back-forward cache. sullivan@chromium.org iclelland@chromium.org haoliuk@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a session window before any soft navigation happens. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 100x the fractional cumulative layout shift score described in the explainer. sullivan@chromium.org iclelland@chromium.org haoliuk@chromium.org An approximation of a high percentile of user interaction latency of a page load before any soft navigation happens, in ms. For this metric, we measure the latency of user interactions as described here: https://web.dev/inp sullivan@chromium.org mmocny@chromium.org johannes@chromium.org Measures the largest contentful paint (https://web.dev/lcp) that has happened prior to any soft navigation. zhouzj@google.com kurtosis-team@google.com Records the number of times a eTLD+1 URL for an ad appears in the last thirty days of history when a page load is initiated from an user activation of an ad. The metric is recorded during an ad page load. zhouzj@google.com kurtosis-team@google.com Records the number of times a URL for an ad appears in the last thirty days of history when a page load is initiated from an user activation of an ad. When querying browser history, the ad's URL is matched without regard to the URL filename, query values, or fragment. The metric is recorded during an ad page load. jkarlin@chromium.org alexmt@chromium.org chrome-analysis-team@google.com Records the time from the top frame navigation until the first ad-frame on the page reaches FirstContentfulPaint. Note that offscreen iframes don't reach FCP until they're scrolled into view, so it can be long. abigailkatcoff@chromium.org chrome-analysis-team@google.com Records the time from the top frame navigation until the first ad-frame on the page reaches FirstContentfulPaint. Only recorded if no Fledge auction (on-device or server) was completed before the frame was painted (but an auction could have been aborted). Note that offscreen iframes don't reach FCP until they're scrolled into view, so it can be long. abigailkatcoff@chromium.org chrome-analysis-team@google.com Records the time from the top frame navigation until the first ad-frame on the page reaches FirstContentfulPaint. Only recorded if both a server and an on-device Fledge auction completed with or without a winner (and was not aborted). This could have been multiple auctions or a single hybrid auction. Note that offscreen iframes don't reach FCP until they're scrolled into view, so it can be long. abigailkatcoff@chromium.org chrome-analysis-team@google.com Records the time from the top frame navigation until the first ad-frame on the page reaches FirstContentfulPaint. Only recorded if a Fledge {AuctionType} auction completed (and was not aborted) and no non-{AuctionType} auction was completed before the frame was painted. {Result} Note that offscreen iframes don't reach FCP until they're scrolled into view, so it can be long. alexmt@chromium.org chrome-ads-histograms@google.com Total number of network bytes that went towards loading non-ad resources for a single page over its entire lifetime. This includes resources that did not finish or were canceled. Only recorded for pages with non-zero total bytes, including those without an ad frame and pages with no ad resources. Recorded when the page is destroyed. alexmt@chromium.org chrome-ads-histograms@google.com The percentage of network bytes loaded by the page that are attributed to ad resources (including ad resources in the main frame) across the entire page load. Only recorded for pages with non-zero network bytes, including those without an ad frame and pages with no ad resources. Recorded when the page is destroyed. alexmt@chromium.org chrome-ads-histograms@google.com The percentage of all bytes loaded by the page that are attributed to ad resources (including ad resources in the main frame) across the entire page load. Only recorded for pages with non-zero total bytes, including those without an ad frame and pages with no ad resources. Recorded when the page is destroyed. yaoxia@chromium.org jkarlin@chromium.org chrome-ads-histograms@google.com The estimated average viewport ad count. This metric takes the average of the ad counts accumulated over the page load time, multiplied by 100 and rounded to the nearest integer. This allows for 2 decimal places of precision. Recorded when the page is destroyed. yaoxia@chromium.org jkarlin@chromium.org chrome-ads-histograms@google.com The estimated average viewport ad density. Each density sample value is calculated as the area of (iframe and img) ads within the viewport * 100 / viewport area, where each overlapping area is counted once. And this metric takes the average of the densities accumulated over the page load time rounded to the nearest integer. Recorded when the page is destroyed. Warning: This histogram has incomplete data. It expired in 08/2025 and was unexpired in 10/2025. jkarlin@chromium.org chrome-ads-histograms@google.com Records whether the heavy ad intervention was disallowed by the blocklist on a frame. Only recorded when the heavy ad blocklist is enabled and available (e.g. this is not recorded in incognito mode). alexmt@chromium.org chrome-ads-histograms@google.com Records the number of network bytes used by a heavy ad unloaded due to network usage by the heavy ad intervention. It is recorded at the time of unload and the value may be larger than the heavy ads threshold due to the delay in unloading an ad. jkarlin@chromium.org chrome-ads-histograms@google.com Total number of network bytes that went towards loading ad resources for a single page over it's entire lifetime. This includes resources that did not finish or were canceled. Only recorded for pages with non-zero ad bytes. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from the user input that triggers the top-level navigation for an AMP document to the time that the navigation for the AMP document is initiated in the AMP frame. This gives insight into how often AMP documents are navigated to via same document navigations without being prerendered. This histogram has incomplete data. It expired after M78 and was re-added in M90. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The number of interactions of a page load, in AMP subframe. Definition of an interaction: https://web.dev/better-responsiveness-metric/#group-events-into-interactions iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The {NormalizedResponsivenessMetric} of a page load, in AMP subframes, in ms. For this metric, we measure the latency of a user interaction by the {UserInteractionLatency} within the user interaction. Full navigation means we only include non-same-document navigations, otherwise we only include same-document navigations. Recorded at the end of the AMP document lifetime, such as when the document is being navigated away from. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in the AMP subframe. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Recorded for non same-document AMP navigations in the main frame, at the end of the AMP document lifetime, such as when the document is being navigated away from. Replaces PageLoad.Clients.AMP.LayoutInstability.MaxCumulativeShiftScore.Subframe.SessionWindow.Gap1000ms.Max5000ms and increases granularity in order to get more coverage for ~40% of the values in the 0-0.1 range. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a {Window}, in the AMP subframe. The gap between two consecutive shifts in a window is not bigger than {Gap} and the maximum window size is {MaxWindowSize}. This metric's integral value is 100x the fractional cumulative layout shift score described in the explainer. If the {Navigation} is FullNavigation, we record the metric for non same-document AMP navigations in the main frame, at the end of the AMP document lifetime, such as when the document is being navigated away from. Otherwise, only same-document navigations are included. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to first "contentful" paint in an AMP subframe document. Will be zero or near-zero in cases where the AMP subframe document was prerendered. Only same-document navigations are included. This histogram has incomplete data. It expired after M78 and was re-added in M90. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to first "contentful" paint in an AMP subframe document. Only non-same-document navigations are included. This histogram has incomplete data. It expired after M78 and was re-added in M90. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to largest "contentful" paint in an AMP subframe document. Only same-document navigations are included. Excludes any content painted after user input. The value is recorded at the end of each page load unless there is an abort or user input before text or image paint. See http://bit.ly/fcp_plus_plus for details. Will be zero or near-zero in cases where the AMP subframe document was prerendered. This histogram has incomplete data. It expired after M78 and was re-added in M90. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org The time from user input to largest "contentful" paint in an AMP subframe document. Only non-same-document navigations are included. Excludes any content painted after user input. The value is recorded at the end of each page load unless there is an abort or user input before text or image paint. See http://bit.ly/fcp_plus_plus for details. This histogram has incomplete data. It expired after M78 and was re-added in M90, also after 2022-12-11 until M111, and also after 2023-06-18 until M121. ryankalla@google.com potassium-anti-fraud-team@google.com Records when a frame from a known CAPTCHA provider is activated by the client. This could mean the user clicked or tapped on the frame. CAPTCHA frames are determined by matching the frame's src url against a list of known CAPTCHA frame url patterns. The list of known CAPTCHA url patterns is served via the component updater. This histogram is split by whether an AI agent was active on the tab at the time of the frame activation. AI agent activity is determined by ActorKeyedService::IsActiveOnTab(), which is used by the Glic Agent. ryankalla@google.com potassium-anti-fraud-team@google.com Records when a frame from {CaptchaProvider} is activated by the client. This could mean the user clicked or tapped on the frame. CAPTCHA frames are determined by matching the frame's src url against a list of known CAPTCHA frame url patterns. The list of known CAPTCHA url patterns is served via the component updater. This histogram is split by whether an AI agent was active on the tab at the time of the frame activation. AI agent activity is determined by ActorKeyedService::IsActiveOnTab(), which is used by the Glic Agent. ryankalla@google.com potassium-anti-fraud-team@google.com Records when a sub-frame is loaded from a known CAPTCHA provider. CAPTCHA frames are determined by matching the frame's src url against a list of known CAPTCHA frame url patterns. The list of known CAPTCHA url patterns is served via the component updater. This histogram is split by whether an AI agent was active on the tab at the time of the frame load. AI agent activity is determined by ActorKeyedService::IsActiveOnTab(), which is used by the Glic Agent. ryankalla@google.com potassium-anti-fraud-team@google.com Records when a sub-frame is loaded from {CaptchaProvider}. CAPTCHA frames are determined by matching the frame's src url against a list of known CAPTCHA frame url patterns. The list of known CAPTCHA url patterns is served via the component updater. This histogram is split by whether an AI agent was active on the tab at the time of the frame load. AI agent activity is determined by ActorKeyedService::IsActiveOnTab(), which is used by the Glic Agent. lbrady@google.com shivanisha@chromium.org dom@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. Recorded on first FencedFrames' page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. shivanisha@chromium.org mparch-dev@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the FencedFrames page (including all subframes). Higher values correspond to greater instability, which is bad. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. On Android it's done when the browser is backgrounded. lbrady@google.com shivanisha@chromium.org dom@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred in the FencedFrames page's main frame. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. On Android, it's done when the browser is backgrounded. shivanisha@chromium.org mparch-dev@chromium.org The time from navigation start to first "contentful" paint. This metric does not include all FencedFrames' page loads. Recorded iff the page loads and the event happens in the foreground. lbrady@google.com shivanisha@chromium.org dom@chromium.org Measures the time from navigation timing's navigation start to the time the first image is painted, for FencedFrames' main frame documents. For images that render progressively, this is recorded as soon as any image pixels have been drawn iff the page loads and the event happens in the foreground. shivanisha@chromium.org mparch-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first paint is performed, for FencedFrames' main frame documents. Recorded iff the page loads and the event happens in the foreground. shivanisha@chromium.org mparch-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames under the FencedFrames root. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. The value is recorded at the end of each page load or the latest time when we can reliably record: when the page is navigated away, the browser is closed, or on Android when the browser is backgrounded, iff the page loads and the event happens in the foreground. suzukikeita@chromium.org chrome-loading@google.com Measures the time for {NavigationCountType} ({BrowserInitializationStatus}) from navigation start to the time the domain lookup ended, for Google Homepage loads. Only recorded for Homepage navigations that start in the foreground and stay in the foreground until domain lookup end. This metric is recorded when the browser finished conducting DNS lookup. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. This histogram has been expired between 2026-05-17 and 2026-07-01, thus does not contain data for this period. suzukikeita@chromium.org chrome-loading@google.com Measures the time for {NavigationCountType} ({BrowserInitializationStatus}) from navigation start to the time the domain lookup started, for Google Homepage loads. Only recorded for Homepage navigations that start in the foreground and stay in the foreground until domain lookup start. This metric is recorded when the browser started to conduct DNS lookup. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. suzukikeita@chromium.org chrome-loading@google.com Measures the time for {NavigationCountType} ({BrowserInitializationStatus}) from navigation start to connect start, for Google Homepage loads. Only recorded for Homepage navigations that start in the foreground and stay in the foreground until connect start. This metric is recorded when the browser started to establish connection. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. suzukikeita@chromium.org chrome-loading@google.com Measures the time for {NavigationCountType} ({BrowserInitializationStatus}) from navigation start to parse start, for Google Homepage loads. Only recorded for Homepage navigations that start in the foreground and stay in the foreground until parse start. This metric is recorded when the parser started. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. yyanagisawa@chromium.org chrome-loading@google.com Whether an Accept-CH frame was received during the connection for the main resource of a main frame navigation, for Google Search page loads. Recorded when the navigation is completed or the app is backgrounded on Android. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) AFT end event is sent, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) AFT end event is sent, including pre-navigation latency (e.g. SGL) but excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the time the DOMContentLoaded event is fired, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the first contentful paint, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the largest contentful paint, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the time the navigation commit request is sent to the renderer, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can start before the beforeunload handler runs to b) when the (existing regular) navigation starts, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the time the parser started, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. bashi@chromium.org chrome-loading@google.com Measures the state of advertised Alt-Svc for a Google search navigation. This is only recorded for Search navigations and is recorded once after navigation commit. suzukikeita@chromium.org chrome-loading@google.com Measures the time from AIO async start to {PerformanceMark}, for Google Search page loads. Records the time between the AIO async start and the timing of {CompletionStatus}. This is only recorded in the outermost main frame, right before the page is being navigated away. suzukikeita@chromium.org chrome-loading@google.com Records whether the {PerformanceMark} was set for Google Search page loads. This is only recorded in the outermost main frame, right before the page is being navigated away. suzukikeita@chromium.org chrome-loading@google.com The possible status of connection reuse for Google search page loads for {Profile} with {ConnectionProtocolType}. This is only recorded for Search navigations and is recorded once after navigation commit. horo@chromium.org chrome-loading@google.com The delay caused by connection establishment for the final HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. horo@chromium.org chrome-loading@google.com The delay caused by domain lookup for the final HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. horo@chromium.org chrome-loading@google.com The delay caused by SSL handshake for the final HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. horo@chromium.org chrome-loading@google.com The delay caused by connection establishment for the first HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. bashi@chromium.org chrome-loading@google.com The coarse connection info used for the DNS-over-HTTPS resolution of the first HTTP request sent for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. bashi@chromium.org chrome-loading@google.com The session source (e.g. new, existing) used for the DNS-over-HTTPS resolution of the first HTTP request sent for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. bashi@chromium.org chrome-loading@google.com The delay caused by domain lookup for the first HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads, when Insecure DNS was used. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. bashi@chromium.org chrome-loading@google.com The delay caused by domain lookup for the first HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads, when Secure DNS (DoH) was used. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. horo@chromium.org chrome-loading@google.com The delay caused by domain lookup for the first HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. bashi@chromium.org chrome-loading@google.com The delay caused by non-caching asynchronous task completion for domain lookup in the first HTTP request sent for the main resource of a main frame navigation, for Google Search page loads, when {ResolutionSource} was used. Only recorded for Search navigations that happen entirely in the foreground. horo@chromium.org chrome-loading@google.com The delay caused by SSL handshake for the first HTTP request which is sent for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. sisidovski@chromium.org chrome-loading@google.com Measures the time {Event}, for Google Search page loads. The recorded values are calculated based on the metrics recorded by the JavaScript, which is done after the navigation commit phase in Search. The metric is emitted when the navigation is completed or the app is backgrounded on Android. This is only recorded in the outermost main frame. Note that this event is randomly sampled based on the JavaScript in the page, recorded at the frequency of 1%. suzukikeita@chromium.org chrome-loading@google.com Measures the time from navigation timing's navigation start to the time the domain lookup ended of {NavigationCountType} ({BrowserInitializationStatus}, {TabInitializationStatus}), for Google Search page loads. Only recorded for Search navigations that start in the foreground and stay in the foreground until domain lookup end. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. suzukikeita@chromium.org chrome-loading@google.com Measures the time from navigation timing's navigation start to the time the domain lookup started of {NavigationCountType} ({BrowserInitializationStatus}, {TabInitializationStatus}), for Google Search page loads. Only recorded for Search navigations that start in the foreground and stay in the foreground until domain lookup start. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. suzukikeita@chromium.org chrome-loading@google.com The number of times a system fallback font was used for {GWSFontFallbackScript} character rendering for a Google Search page load, {GWSFontLoadingMilestone}. Recorded in batch at the milestone. suzukikeita@chromium.org chrome-loading@google.com The number of times a system fallback font was used for character rendering for a Google Search page load, {GWSFontLoadingMilestone}. suzukikeita@chromium.org chrome-loading@google.com The cumulative duration spent in system fallback font loading for character rendering for a Google Search page load, {GWSFontLoadingMilestone}. suzukikeita@chromium.org chrome-loading@google.com The duration of the very first system fallback font load for character rendering during the lifetime of a Google Search page load. Recorded when the page load is completed. suzukikeita@chromium.org chrome-loading@google.com The hit rate (hits / (hits + misses)) of the NGShapeCache up to First Contentful Paint (FCP) for a Google Search page load. Recorded when FCP is reached. toyoshim@chromium.org chrome-loading@google.com Records the number of page loads that the user has done in the current session. This is recorded once per session when the user closes the last tab {SessionType}. suzukikeita@chromium.org chrome-loading@google.com The status of whether the DSEPrewarm feature was ever triggered on the same renderer process host. This is recorded once, when a Google search page is committed for {InitiatorOfNavigation} and {PrerenderStatus}. bashi@chromium.org chrome-loading@google.com Measures whether QUIC is enabled at the network stack for Google search navigation. This is only recorded for Search navigations and is recorded once after navigation commit. suzukikeita@chromium.org chrome-loading@google.com The HTTP status code of Google search page loads for {NavigationType} {IncognitoSuffix}. This is only recorded for Search navigations and is recorded OnRedirect and OnCommit. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the OS-level timestamp of the user input event that started a navigation to b) when the "actual" navigation starts. Recorded at the point when a navigation finishes committing, i.e. finishes processing the DidCommitNavigation message. This is recorded only for main frame cross-document Google Search Page navigations where the user interaction timestamp is available. gjc@google.com chrome-loading@google.com Measures the duration from a) the OS-level timestamp of the user input event that started a navigation to b) when the Above the Fold (AFT) content is fully rendered, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the OS-level timestamp of the user input event that started a navigation to b) when the navigation starts, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for Google Search page loads. suzukikeita@chromium.org chrome-loading@google.com Records whether the first navigation is the navigation to GWS or not. This is recorded for the first navigation after the browser init, at commit. True indicates that the first navigation after browser init is to GWS, while as False indicates that the navigation was for elsewhere. sisidovski@chromium.org rakina@chromium.org chrome-loading@google.com The time relative to the milestone {NavigationMilestone} that a navigation gets abandoned due to {NavigationAbandonReason}, on a main frame navigation for SRP navigations. Abandonment from backgrounding or hiding are non-terminal, while other abandonment for other reasons are terminal. This means this metric might be recorded multiple times if the navigation is only abandoned non-terminally before, but only once for each abandonment reason. Metrics logged after non-terminal abandonment will be marked with the suffixes {BackgroundSuffix} and/or {HiddenSuffix}. The milestone recorded will be the latest milestone (if there are multiple milestones reached before the abandonment). The metric is emitted when the navigation gets abandoned. The "ResponseFromCache" variant was disabled during M141. chikamune@chromium.org chrome-loading@google.com Records the execution mode of the beforeunload handlers for a Google Search navigation. This is a GWS-specific version of PageLoad.Navigation.BeforeUnloadExecutionMode{SameOrCrossOrigin}. Recorded at the time of navigation commit for cross-document {SameOrCrossOrigin} outermost main frame navigations. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the time the navigation commit request is sent to the renderer to b) the time the renderer starts parsing the HTML. This is recorded for Google Search page loads. suzukikeita@chromium.org chrome-loading@google.com The type of source which the navigation started from, for Google Search page loads. This is only recorded for Search navigations and is recorded once after navigation commit. This metric is recorded {ConnectionReuseStatus}. chikamune@chromium.org chrome-loading@google.com The time relative to navigation start that navigation commit message for a main frame navigation is sent to a renderer process. This is recorded for Google Search page loads. hayato@chromium.org chrome-loading@google.com Measures the time taken to call http network transaction connected callback, for Google Search page loads. Recorded every time the connected callback is called and completed, for Google Search page loads. Emitted when the navigation is completed or the app is backgrounded on Android. hayato@chromium.org chrome-loading@google.com The time taken for HTTP stream creation to finish, for Google Search page loads. Recorded every time HttpStream::CreateStream() is called, for Google Search page loads. Emitted when the navigation is completed or the app is backgrounded on Android. bashi@chromium.org chrome-loading@google.com Measures elapsed time from eligibility check in BeginNavigationImpl to the first fetch start time for eligible navigations, for Google Search page loads. bashi@chromium.org chrome-loading@google.com Measures elapsed time from eligibility check in BeginNavigationImpl to loader start time for eligible navigations, for Google Search page loads. yyanagisawa@chromium.org chrome-loading@google.com The time from the final HTTP request start to the final HTTP response start for the main resource of a main frame navigation, for Google Search page loads. This measures the network latency of the final request, including any potential delay from offloading client hints checks to the network layer. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. hayato@chromium.org chrome-loading@google.com Measures the time from navigation timing's first fetch start, the browser is ready to fetch the first HTTP request, to the first request start, the time the first HTTP request was sent for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. yyanagisawa@chromium.org chrome-loading@google.com The time from the first HTTP request start to the final HTTP response start for the main resource of a main frame navigation, for Google Search page loads. This measures the total network latency across all redirects, including any potential delay from offloading client hints checks to the network layer. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. yyanagisawa@chromium.org chrome-loading@google.com The time from the first HTTP request start to the first HTTP response start for the main resource of a main frame navigation, for Google Search page loads. This measures the network latency of the first request, including any potential delay from offloading client hints checks to the network layer. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. hayato@chromium.org chrome-loading@google.com The time taken for HTTP stream initialization to finish if the initialization was blocked, otherwise zero, for Google Search page loads. Recorded every time HttpStream::InitializeStream() is called, for Google Search page loads. Emitted when the navigation is completed or the app is backgrounded on Android. bashi@chromium.org chrome-loading@google.com The delay caused by waiting for stream limit for the main resource of a main frame navigation, for Google Search page loads with {ConnectionProtocolType}. Only recorded for Search navigations. The metric is emitted when the navigation is completed or the app is backgrounded on Android. nidhijaju@chromium.org chrome-loading@google.com The time relative to navigation start that a callback for the navigation loader is last invoked for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. nidhijaju@chromium.org chrome-loading@google.com The time relative to navigation start that the final HTTP request is sent for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. nidhijaju@chromium.org chrome-loading@google.com The time relative to navigation start that the headers of the final HTTP response is received for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. nidhijaju@chromium.org chrome-loading@google.com The time relative to navigation start that the browser is ready to fetch the first HTTP request, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. kouhei@chromium.org chrome-loading@google.com The time relative to navigation start that a callback for the navigation loader is first invoked for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. kouhei@chromium.org chrome-loading@google.com The time relative to navigation start that the first HTTP request is sent for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. kouhei@chromium.org chrome-loading@google.com The time relative to navigation start that the headers of the first HTTP response is received for the main resource of a main frame navigation, for Google Search page loads. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. suzukikeita@chromium.org chrome-loading@google.com The time relative to navigation start that the page load metrics observer is destructed (i.e. the page is closed), for Google Search page loads. The metric is emitted when the navigation is completed. suzukikeita@chromium.org chrome-loading@google.com Measures the time from navigation timing's navigation start to the time the navigation start of {NavigationCountType} ({BrowserInitializationStatus}, {TabInitializationStatus}), for Google Search page loads. Only recorded for Search navigations that start in the foreground and stay in the foreground until connect start. In cases where navigation start occurs after connect start (e.g. pre-fetch, pre-connect), this metric will contain zero. yyanagisawa@chromium.org chrome-loading@google.com Whether the connected callback was called during the connection for the main resource of a main frame navigation, for Google Search page loads. Recorded when the navigation is completed or the app is backgrounded on Android. lingqi@chromium.org chikamune@chromium.org chrome-loading@google.com Similar to PageLoad.Clients.GoogleSearch.PaintTiming.AFTEndWithPreNavigationLatency, but only track traverse navigations, with the breakdown of {TraverseRestoreType}. Note that as of M148, this metric will no longer contain non-activated, prerender navigations (which was the case before the fix). annasato@chromium.org chrome-loading@google.com Recorded when the first contentful paint (FCP) occurs on a Google Search page load. Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints content, for Google Search page loads where subsequent duplicate navigation requests were ignored. Only recorded for Search navigations that start in the foreground and stay in the foreground until the first contentful paint. spelchat@chromium.org chrome-brapp-loading@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints content, for Google Search page loads {SyntheticResponseSuffix}. A contentful paint includes a paint of text, image, SVG, or canvas. Only recorded for Search navigations that start in the foreground and stay in the foreground until the first contentful paint. spelchat@chromium.org chrome-brapp-loading@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the experimental largest content (text or image) within viewport, for Google Search page loads. See http://bit.ly/largest_contentful_paint_explainer for more details. Differs from SubFrame.PaintTiming.NavigationToLargestContentfulPaint in that removed content is still considered a valid candidate. Only recorded for Search navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. lingqi@chromium.org chrome-prerendering@google.com Similar to PageLoad.Clients.GoogleSearch.PaintTiming.NavigationToLargestContentfulPaint, but only recorded when the navigation was started from the context menu. lingqi@chromium.org chikamune@chromium.org chrome-loading@google.com Similar to PageLoad.Clients.GoogleSearch.PaintTiming.NavigationToLargestContentfulPaint, but only track traverse navigations, with the breakdown of {TraverseRestoreType}. sisidovski@chromium.org chrome-loading@google.com Measures the time from navigation start to the time {MileStone}, for Google Search page loads on {PageLoadType} with {IncognitoSuffix}{SyntheticResponseSuffix}. The actual value is recorded via `startTime` in performance.mark()'s markOptions. If `startTime` is not set, this metric is not recorded. This is recorded by emitting `performance.mark()` in JavaScript, which is done after the navigation commit phase in Search. This is only recorded in the outermost main frame. chikamune@chromium.org chrome-loading@google.com Measures the duration from the time the renderer starts parsing the HTML to the time the DOMContentLoaded event is fired. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the time from when the HTML parser started, to when the page first paints content. This is recorded for Google Search page loads. chikamune@chromium.org chrome-loading@google.com Measures the duration from the time the renderer starts parsing the HTML to the time the largest contentful paint occurs. This is recorded for Google Search page loads. kouhei@chromium.org chrome-loading@google.com Measures the time from navigation timing's navigation start to the time the parser started, for Google Search page loads{SyntheticResponseSuffix}. Only recorded for Search navigations that start in the foreground and stay in the foreground until parse start. This metric has incomplete data. It was expired between 2023-10-01 and M121. suzukikeita@chromium.org chrome-loading@google.com Measures the time from when a prerendered page is activated to the first contentful paint, for GWS page loads for {IncognitoSuffix}. Only recorded for GWS navigations that were prerendered and activated. suzukikeita@chromium.org chrome-loading@google.com Measures the time from when a prerendered page is activated to the largest contentful paint, for GWS page loads for {IncognitoSuffix}. Only recorded for GWS navigations that were prerendered and activated. suzukikeita@chromium.org chrome-loading@google.com Whether the prerendering navigation is reusing a prerender host or not for {IncognitoSuffix}. This is recorded once, when a prerendered page is activated for Google search page loads. suzukikeita@chromium.org chrome-loading@google.com Measures the time from when a initial prerender navigation starts in the background to when the prerendered page is activated, for GWS page loads for {IncognitoSuffix}. Only recorded for GWS navigations that were prerendered and activated. suzukikeita@chromium.org chrome-loading@google.com The status of whether the DSEPrewarm feature was triggered before the prerender host reuse happened. This is recorded once, when a prerendered page is activated for Google search page loads for {InitiatorOfNavigation} and {PrerenderStatus}. suzukikeita@chromium.org chrome-loading@google.com Records whether the Google Search prewarm page load was served from the HTTP cache or network. Recorded once upon navigation commit of the prerendered prewarm page. bashi@chromium.org chrome-loading@google.com Measures whether a navigation for Google search uses a new session or an existing session with {ConnectionProtocolType}. This is only recorded for Search navigations and is recorded once after navigation commit. Note that this is only recorded for HTTP/2 and HTTP/3. suzukikeita@chromium.org chrome-loading@google.com Records how the main frame's SiteInstance was assigned a renderer process. This is recorded once, when a Google search page is committed for {InitiatorOfNavigation} and {PrerenderStatus}. toyoshim@chromium.org chrome-loading@google.com Records the current cookie warm-up type of the browser session for the Google search page. This metric is emitted when the navigation is completed or the app is backgrounded on Android. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the confidence value of ElementLocator that {PositiveOrNegative} actually. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records a value (10 * normalized_total_frequency_0_to_9 + normalized_confidence_0_to_9) of ElementLocator per total-frequency that {PositiveOrNegative} actually. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the frequency value of ElementLocator that {PositiveOrNegative} actually. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records a value (10 * normalized_confidence_0_to_9 + normalized_total_frequency_0_to_9) of ElementLocator per confidence that {PositiveOrNegative} actually. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the total frequency of ElementLocator that {PositiveOrNegative} actually and it also has a confidence value between {Range}. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the actual index in learned element locators ordered by frequency up to "max_lcpp_histogram_buckets" in LCP timing prediction. If actual LCP is out of locators, that is recorded as "max_lcpp_histogram_buckets" + 1 value. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records if the actual LCP element is image or not. This metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. kouhei@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Measures the time from navigation start to the first contentful paint. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data. kouhei@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Measures the time from navigation start to the largest contentful paint. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the hit index in learned element locators ordered by frequency up to "max_lcpp_histogram_buckets" when LCP timing predictor succeeded. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the result of LCP timing predictor. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Measures the time from navigation start to the largest contentful paint. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCPP prediction succeeded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records a value (10 * normalized_total_frequency_0_to_9 + normalized_confidence_0_to_9) of {Site} subresource url per total-frequency that {PositiveOrNegative} actually. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the confidence value of {Site} subresource url that {PositiveOrNegative}. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the subresource prediction precision of LCP critical path predictor (LCPP). For example, If LCPP predicts subresource type A, B, C and D for a page and the page actually loads A and E before LCP, then precision = [A] / [A, B, C, D] = 25%, and recall = [A] / [A, E] = 50%. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the subresource prediction recall of LCP critical path predictor (LCPP). For example, If LCPP predicts subresource type A, B, C and D for a page and the page actually loads A and E before LCP, then precision = [A] / [A, B, C, D] = 25%, and recall = [A] / [A, E] = 50%. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the subresource's same site ratio of LCP critical path predictor (LCPP). The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. yoichio@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the subresource type distribution of LCP critical path predictor (LCPP). The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only once when the user navigates away from the page. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the frequency value of {Site} subresource url that {PositiveOrNegative}. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records a value (10 * normalized_confidence_0_to_9 + normalized_total_frequency_0_to_9) of {Site} subresource url per confidence that {PositiveOrNegative} actually. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org src/third_party/blink/renderer/core/lcp_critical_path_predictor/OWNERS Records the total frequency of {Site} subresource url that {PositiveOrNegative} actually and it also has a confidence value between {Range}. The metric is emitted only for navigations that LCP Critical Path Predictor provided non-empty hint data and only when LCP is recorded. chikamune@chromium.org chrome-loading@google.com {Timing} {OtherLoadingCount} {Background} awillia@chromium.org sergiog@microsoft.com src/components/page_load_metrics/OWNERS Determines if a navigation has not been completed due to not resulting in painted content before the maximum timeout allowed. The histogram will be emitted with true value once timeout expires and first contentful paint is not reached, and it will be emitted with false value if first contentful paint is reached before expiring the timeout. The navigation is considered as suspended, and thus the timeout timer will be stopped, when page is going to back and forward cache or is hidden. Timeout timer will be restarted when page is restored from back and forward cache or is back to shown from hidden and first contentful paint was not yet reached. In case that navigation is started in background, the timeout timer will not be started until the page is moved to foreground. joenotcharles@google.com catan-team@chromium.org Recorded for each navigation when its PerformanceManager loading state reaches PageNode::LoadingState::kLoadedIdle, with the time since navigation start. If a navigation is abandoned without ever reaching kLoadedIdle, PageLoad.Clients.PerformanceManager.NavigationWithoutLoadedIdle is recorded instead. This version of the metric is recorded for navigations in {LoadedIdleVisibility}. joenotcharles@google.com catan-team@chromium.org Recorded for each navigation that's abandoned without its PerformanceManager loading state reaching PageNode::LoadingState::kLoadedIdle, such as by the page closing or a new navigation starting. The value is the time from navigation start to the time it's abandoned. If the navigation reaches kLoadedIdle, PageLoad.Clients.PerformanceManager.NavigateToLoadedIdle is recorded instead. This version of the metric is recorded for navigations in {LoadedIdleVisibility}. suzukikeita@chromium.org src/content/browser/preloading/prerender/OWNERS Whether the prerendering navigation is reusing a prerender host or not. This is recorded once, when a prerendered page is activated. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.InteractiveTiming.FirstInputDelay4, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.InteractiveTiming.FirstInputDelay4. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.LayoutInstability.CumulativeShiftScore.MainFrame, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.LayoutInstability.CumulativeShiftScore.MainFrame. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.LayoutInstability.CumulativeShiftScore, but for page loads that were prerendered and were later activated. Note that prerendered page loads are excluded from PageLoad.LayoutInstability.CumulativeShiftScore. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS Measures the time from the start of initial prerendering navigation to the start of activation navigation. This corresponds to the activationStart attribute of PerformanceNavigationTiming. Recorded when a prerendered page is activated. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.PaintTiming.NavigationToFirstContentfulPaint, but for page loads that were prerendered and were later activated. This measures the time relative to the activation navigation start. Note that prerendered page loads are excluded from PageLoad.PaintTiming.NavigationToFirstContentfulPaint. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.PaintTiming.NavigationToFirstPaint, but for page loads that were prerendered and were later activated. This measures the time relative to the activation navigation start. Note that prerendered page loads are excluded from PageLoad.PaintTiming.NavigationToFirstPaint. nhiroki@chromium.org src/content/browser/preloading/prerender/OWNERS PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, but for page loads that were prerendered and were later activated. This measures the time relative to the activation navigation start. Note that prerendered page loads are excluded from PageLoad.PaintTiming.NavigationToLargestContentfulPaint2. linnan@chromium.org measurement-api-dev+metrics@google.com PageLoad.InteractiveTiming.FirstInputDelay4, but recorded iff {PrivacySandboxAdsApi} was used in the page. linnan@chromium.org measurement-api-dev+metrics@google.com PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2, but recorded iff {PrivacySandboxAdsApi} was used in the page. linnan@chromium.org measurement-api-dev+metrics@google.com PageLoad.PaintTiming.NavigationToFirstContentfulPaint, but recorded iff {PrivacySandboxAdsApi} was used in the page. linnan@chromium.org measurement-api-dev+metrics@google.com PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, but recorded iff {PrivacySandboxAdsApi} was used in the page. sisidovski@chromium.org chrome-worker@google.com The {Timing} time of pages with the Service Worker fetch handlers. Metrics won't be recorded if pages are not controlled by service workers. This is recorded only when the ServiceWorker script is eligible for the experiment. Warning: this histogram was expired from 2024-07-21 to 2024-11-18. sisidovski@chromium.org chrome-worker@google.com The {Timing} time of pages with the Service Worker fetch handlers. Metrics won't be recorded if pages are not controlled by service workers. This is recorded only when the response is created with the synthetic response. yyanagisawa@chromium.org chrome-worker@google.com The {Timing} time of pages with the Service Worker fetch handlers. Metrics won't be recorded if pages are not controlled by service workers. The metrics are broken down by {HandlerType}. {HandlerType} only explains the page's handler type, and it does not mean the fetch handler is actually skipped or not. sisidovski@chromium.org chrome-worker@google.com Measures the time from navigation timing's navigation start to the time the parser started, for page controlled by service worker{SyntheticResponseSuffix}. Only recorded for navigations that start in the foreground and stay in the foreground until parse start. This metric is emitted when the parser starts for a navigation. jkarlin@chromium.org chrome-ads-histograms@google.com The time from navigation start to the first contentful paint of third-party (in respect to scheme://eTLD+1) frames on pages. Note that this can be significantly delayed due to lazy loading. Note also that all of the PageLoad.Clients.ThirdParty.Frames metrics will only be recorded for the first kMaxRecordedFrames (50) active iframe RenderFrameHosts (at any given time). awillia@chromium.org djmitche@chromium.org The time from navigation start to the first contentful paint of third-party opaque origin frames on pages. Note that this metric is only collected when the top-level origin is not opaque. Also, this metric can be significantly delayed due to lazy loading. Note also that all of the PageLoad.Clients.ThirdParty.Frames metrics will only be recorded for the first kMaxRecordedFrames (50) active iframe RenderFrameHosts (at any given time). awillia@chromium.org djmitche@chromium.org The time from navigation start to the largest contentful paint of third-party opaque origin frames on pages. Note that this metric is only collected when the top-level origin is not opaque. Note also that all of the PageLoad.Clients.ThirdParty.Frames metrics will only be recorded for the first kMaxRecordedFrames (50) active iframe RenderFrameHosts (at any given time). jkarlin@chromium.org yaoxia@chromium.org The number of third party (in respect to scheme://eTLD+1) origins on a page that read cookies either via resource request headers or document.cookie. This metric was expired between May and August 2023 and may be missing data. narms@google.com android-sre@google.com The result of attempting to load a page. Logs a success when the load reaches FirstContentfulPaint without being backgrounded, or a different result if the load ends before that for any reason. This histogram is intended to track the success rate of page loads in WebView, and only logs page loads while they are in the foreground. narms@google.com android-sre@google.com The count of page loads that were attempted in WebView. This histogram is intended to track the success rate of page loads in WebView, and only logs page loads that start in the foreground. This histogram logs when a navigation is started and only logs to the "true" bucket. nidhijaju@chromium.org blink-network-stack@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints content, for page loads that can use zstd. A contentful paint includes a paint of text, image, SVG, or canvas. Only recorded for navigations that start in the foreground and stay in the foreground until the first contentful paint. nidhijaju@chromium.org blink-network-stack@google.com Measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the experimental largest content (text or image) within viewport, for page loads that can use zstd. See https://github.com/w3c/largest-contentful-paint for more details. Differs from SubFrame.PaintTiming.NavigationToLargestContentfulPaint in that removed content is still considered a valid candidate. Only recorded for navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. nidhijaju@chromium.org blink-network-stack@google.com Measures the time from navigation timing's navigation start to the time the parser started, for page loads that can use zstd. Only recorded for navigations that start in the foreground and stay in the foreground until parse start. This metric is emitted when the parser starts for a navigation. Warning: this histogram was expired from 2025-04-07 to 2025-06-25; data may be missing. chikamune@chromium.org loading-dev@chromium.org {MetricName}, but recorded only for {Origin} navigations. sisidovski@chromium.org rakina@chromium.org chrome-loading@google.com Logs the navigation abandonment reason that happens when the last milestone is {NavigationMilestone} on a main frame navigation for {ObservedNavigation} with {ResponseFromCache} connection, with potentially some suffixes detaling the navigation {BackgroundSuffix}, {IncognitoSuffix} and/or {HiddenSuffix} . The metric is emitted when the navigation gets abandoned. sisidovski@chromium.org rakina@chromium.org chrome-loading@google.com Logs the last navigation milestone reason that was reached when a main frame navigation for {ObservedNavigation} is abandoned due to {NavigationAbandonReason}, with potentially some suffixes detaling the navigation {BackgroundSuffix}, {IncognitoSuffix} and/or {HiddenSuffix} . The metric is emitted when the navigation gets abandoned. sisidovski@chromium.org rakina@chromium.org chrome-loading@google.com The time relative to the navigation start that the final renderer process is created for a main frame navigation for {ObservedNavigation} with potentially some suffixes detaling the navigation {BackgroundSuffix}, {HiddenSuffix}, {IncognitoSuffix}, {ResponseFromCache}. The metric is emitted when the navigation's commit IPC is just sent out, if the renderer process is created after the navigation started. rakina@chromium.org chrome-loading@google.com The time relative to navigation start that a navigation reaches the the milestone {NavigationMilestone} on a main frame navigation for {ObservedNavigation}, with potentially some suffixes detaling the navigation {BackgroundSuffix}, {HiddenSuffix}, {IncognitoSuffix}, {ResponseFromCache}. Only recorded for Search navigations that didn't get terminally abandoned at least until the relevant milestone. Note that abandonment from backgrounding or hiding are non-terminal, so milestones after those types of abandonments will still be logged. The metric is emitted when the navigation finishes committing or it gets abandoned (which can happen multiple times during the navigation if non-terminal, so only the milestones that haven't been logged will be logged). rakina@chromium.org chrome-loading@google.com The time relative to navigation start that a navigation takes to emit this metric, on a main frame navigation for {ObservedNavigation}. The metric is emitted when the navigation finishes committing or it gets abandoned for the first time. sisidovski@chromium.org chrome-loading@google.com Network status codes recorded for the abandoned navigation request, with potentially some suffixes detaling the navigation {BackgroundSuffix}, {HiddenSuffix}, {IncognitoSuffix}, {ResponseFromCache}. The metric is emitted when the navigation gets abandoned. sisidovski@chromium.org rakina@chromium.org chrome-loading@google.com Whether the renderer process for the navigation is already created before the navigation start or not, for a main frame navigation for {ObservedNavigation} with potentially some suffixes detaling the navigation {BackgroundSuffix}, {HiddenSuffix}, {IncognitoSuffix}, {ResponseFromCache}. The metric is emitted when the navigation's commit IPC is just sent out. sisidovski@chromium.org chrome-loading@google.com The Duration from the navigation start time to the time that a navigation gets abandoned after the milestone {NavigationMilestone} on a main frame navigation for {ObservedNavigation} with {ResponseFromCache}. Only the abandonments due to backgrounding and hiding are non-terminal, and other abandonments are terminal. This means this metric might be recorded multiple times if the navigation is only abandoned non-terminally before, but only once for each abandonment reason. "This is logged after non-terminal abandonment of pages which were {BackgroundSuffix}, {HiddenSuffix} and {IncognitoSuffix}. The milestone recorded will be the latest milestone (if there are multiple milestones reached before the abandonment). The metric is emitted when the navigation gets abandoned. sisidovski@chromium.org rakina@chromium.org chrome-loading@google.com For a navigation of type {NavigationType} that gets abandoned due to {NavigationAbandonReason} from the navigation's start time, for a main frame navigation for {ObservedNavigation} with {ResponseFromCache} connection, with potentially some suffixes detaling the navigation {BackgroundSuffix}, {HiddenSuffix} and/or {IncognitoSuffix}. The metric is emitted when the navigation gets abandoned. anunoy@chromium.org For each page load, records whether the page is a search results page from the default search engine. Recorded at the time of commit. suzukikeita@chromium.org chrome-loading@google.com The delay caused by connection establishment for the first HTTP request which is sent for the main resource of a main frame navigation. Only recorded for navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. suzukikeita@chromium.org chrome-loading@google.com The delay caused by domain lookup for the first HTTP request which is sent for the main resource of a main frame navigation. Only recorded for navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. suzukikeita@chromium.org chrome-loading@google.com The delay caused by SSL handshake for the first HTTP request which is sent for the main resource of a main frame navigation. Only recorded for navigations that happen entirely in the foreground. The metric is emitted when the navigation is completed or the app is backgrounded on Android. This histogram has been expired between 2026-05-03 and 2026-07-01, thus does not contain data for this period. alexmt@chromium.org chrome-ads-histograms@google.com Recorded when the page is destroyed or the app is backgrounded on mobile. Records the total wall time of tasks attributable to the page across its lifetime. Considers both the CPU usage while the page is in the foreground and in the background. alexmt@chromium.org chrome-ads-histograms@google.com Recorded when the page is destroyed or the app is backgrounded on mobile. Records the total wall time of tasks attributable to the page across its lifetime. Does not consider CPU usage while a page is backgrounded. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the time the DOMContentLoaded event is fired, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each page load. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the DOMContentLoaded event is fired, for main frame documents. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the load event is fired, for main frame documents. chikamune@chromium.org chrome-loading@google.com Measures the duration from the time the renderer starts parsing the HTML to the time the DOMContentLoaded event is fired. This is recorded for each page load. dougarnett@chromium.org tbansal@chromium.org sullivan@chromium.org The maximum size click input burst for the page load. A click input burst is a sequence of user click inputs at approximately the same screen position where the clicks each occur soon after the previous one (e.g., within half second). This is intended to detect possible rage clicks by the user. Note: stat collection stopped in August 2021, and resumes in February 2023. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level input event that initiated a navigation, and the navigation actually starting. chikamune@chromium.org chrome-loading@google.com Records true if PageLoad.Experimental.InputTiming.InputToNavigationStart is recorded for a {InitiatorOfNavigation} {WithOrWithoutUserGesture}, and false otherwise. This is recorded when the navigation actually starting. chikamune@chromium.org chrome-loading@google.com The time between the OS-level input event and navigation start, for the form-submit in the renderer. This is recorded when the navigation actually starting. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level click/tap event and navigation start, for clicks on links in the renderer. spelchat@chromium.org chrome-brapp-loading@google.com The time between the OS-level keypress/tap event in the omnibox and navigation start, for navigations from the omnibox. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that a callback for the navigation loader is last invoked for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the headers of the final HTTP response is received for the main resource of a main frame navigation. This metric has incomplete data. It was expired between 2022-12-18 and M121. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that a callback for the navigation loader is first invoked for the main resource of a main frame navigation. This metric has incomplete data. It was expired between 2023-07-09 and M121. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the first HTTP request is sent for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that the headers of the first HTTP response is received for the main resource of a main frame navigation. nhiroki@chromium.org chrome-loading@google.com The time relative to navigation start that navigation commit message for a main frame navigation is sent to a renderer process. horo@chromium.org chrome-loading@google.com Measures the time from load start to when headers have been received for resource requests which come from the cache. Logged for every {RequestDestination} resource request from the cache. This metric has incomplete data. It was expired after 2023-08-07 until M121, and also after 2024-02-09 until M142. cduvall@chromium.org jam@chromium.org Measures the time from when the navigation commit was sent to the renderer to the first subresource load start. Logged for every page load which has subresources. This metric has incomplete data. It was expired between 2023-02-12 and M121. cduvall@chromium.org jam@chromium.org Measures the time from navigation start to the first subresource load start. Logged for every page load which has subresources. cduvall@chromium.org jam@chromium.org Measures the time from load start to when headers have been received for resource requests which do not come from the cache. Logged for every {RequestDestination} resource request which is not from the cache. sullivan@chromium.org speed-metrics-dev@chromium.org Determines the final status for this page load. That is, records whether the page was never foregrounded, was foregrounded but did not reach FCP, or did reach FCP. The metric is recorded at the end of each page load. As usual with PageLoad metrics, we consider app backgrounding on Android to be the end of page load as well as the app could be evicted by Android anytime after that happens. sullivan@chromium.org speed-metrics-dev@chromium.org The time between the OS-level input event that initiated a navigation, and the first contentful paint of the page that was loaded in the navigation. iclelland@chromium.org speed-metrics-dev@chromium.org Records the number of soft navigations detected during a page load. Recorded by the SoftNavigationPageLoadMetricsObserver each time the page enters the back/forward cache, and also when the page is destroyed, with the number of soft navigations observed since the last recording. npm@chromium.org speed-metrics-dev@chromium.org chrome-prerendering@google.com The total amount of time the page spent in the foreground. Note that this metric adds all foreground durations occurring for the page. For example: if the page starts foregrounded during 1 second, then goes to the background for a while, then is foregrounded again for 2 seconds, and then is unloaded, this metric reports 3 seconds. The metric is recorded at the end of each page load. As usual with PageLoad metrics, we consider app backgrounding on Android to be the end of page load as well as the app could be evicted by Android anytime after that happens. hajimehoshi@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per back-forward navigation. Recorded on first page interaction after the page is restored from the back-forward cache. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay4. These two histograms will be aggregated on the server to form the authoritative metric. hajimehoshi@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org iOS only. This is the same as PageLoad.InteractiveTiming.FirstInputDelay.AfterBackForwardCacheRestore, but uses the same bucketing on iOS as non-iOS platforms use in that metric. Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per back-forward navigation. Recorded on first page interaction after the page is restored from the back-forward cache. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay4_iOSFixed. These two histograms will be aggregated on the server to form the authoritative metric. sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay.AfterBackForwardCacheRestore. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com iOS only. This is the same as PageLoad.InteractiveTiming.FirstInputDelay4, but uses the same bucketing on iOS as non-iOS platforms use in that metric. Measures First Input Delay, the duration between the hardware timestamp and the start of event processing on the main thread for the first meaningful input per navigation. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.InteractiveTiming.FirstInputDelay.AfterBackForwardCacheRestore_iOSFixed. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org The duration between navigation start and the hardware timestamp of the first meaningful input per navigation. Recorded on first page interaction. See https://goo.gl/tr1oTZ for a detailed explanation. Excludes scrolls. sullivan@chromium.org speed-metrics-dev@chromium.org The one-based offset of the interaction that is the INP (https://web.dev/inp). sullivan@chromium.org speed-metrics-dev@chromium.org The time, relative to navigation start, of the interaction that is the INP (https://web.dev/inp). sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The duration between the hardware timestamp and the start of event processing on the main thread for a meaningful input. Excludes scrolls. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. WARNING: The long tail of this metric is buggy on Mac (overflows for a subset of users) which can lead to surprising false regressions or improvements. sullivan@chromium.org speed-metrics-dev@chromium.org The duration between navigation start and the hardware timestamp of a meaningful input. Excludes scrolls. sullivan@chromium.org speed-metrics-dev@chromium.org The number of user interactions in a {PageLoadType} page load. Definition of interaction: https://web.dev/better-responsiveness-metric/#group-events-into-interactions iclelland@chromium.org speed-metrics-dev@chromium.org The duration between the start of event processing and the end of event processing on the main thread for a meaningful input. Excludes scrolls. This metric is recorded when users interact with the page, which may trigger input events such as pointerdown, keydown, click and mousedown. iclelland@chromium.org speed-metrics-dev@chromium.org The duration between the end of event processing and the time when the first paint was performed on the main thread for a meaningful input. Excludes scrolls. This metric is recorded when users interact with the page, which may trigger input events such as pointerdown, keydown, click and mousedown. iclelland@chromium.org speed-metrics-dev@chromium.org The {NormalizedResponsivenessMetric} of a {PageLoadType} page load, in ms. For this metric, we measure the latency of a user interaction by the {UserInteractionLatency} within the user interaction. Recorded at the end of the page load lifetime, such as when users navigate to a new web page, except UserInteractionLatencyAtFirstOnHidden.HighPercentile2, which is recorded when a page is moved from the foreground to the background for the first time. UserInteractionLatencyAtFirstOnHidden.HighPercentile2 is trying to record the INP values which are not able to be recorded in UserInteractionLatency.HighPercentile2 for some reasons. csharrison@chromium.org bmcquade@chromium.org Counts of various internal error conditions in the page_load_metrics system. toyoshim@chromium.org src/components/page_load_metrics/OWNERS src/content/browser/preloading/prerender/OWNERS The status of validity check of PageLoadTiming structs received from the render process over IPC. Recorded when timing information is {Condition}. Warning: this histogram was expired from 2021-01-31 to 2023-01-13; data may be missing. iclelland@chromium.org speed-metrics-dev@chromium.org Measures whether the largest contentful paint, whose timestamp is measured by PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, comes from text or image. This value is recorded whenever PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 is recorded. iclelland@chromium.org speed-metrics-dev@chromium.org Measures whether the largest contentful paint in the main frame, whose timestamp is measured by PageLoad.PaintTiming.NavigationToLargestContentfulPaint2.MainFrame, comes from text or image. This value is recorded whenever PageLoad.PaintTiming.NavigationToLargestContentfulPaint2.MainFrame is recorded. lingqi@chromium.org chrome-prerendering@google.com Records error codes for loading of a main resource of a main frame which belongs to a prerendered and then activated page when the page received loading completion event for the resource. This metric is used to monitor whether preload cache intercepting logic causes extra page loading errors. lingqi@chromium.org chrome-prerendering@google.com Records the duration from DOMContentLoaded to activation for a prerendered and then activated page. Note that the duration is shifted by 1 minute (60000ms) when recording the metric, because UMA cannot record negative values. If the DOMContentLoaded event is fired after activation, the number will be less than 60000(ms). If the DOMContentLoaded event is fired before activation, the number will be greater than 60000(ms). This metric will be recorded when a session ends, at PrerenderPageLoadMetricsObserver::MaybeRecordDocumentLoadMetrics. kenoss@chromium.org src/content/browser/preloading/prerender/OWNERS Counts page load events related to Prerender2, like navigation in prerendered main frame and prerendering activation navigation. Recorded when those events are observed in PageLoadTracker. lingqi@chromium.org chrome-prerendering@google.com Records the duration from when to start parsing main resource to activation for a prerenderedand then activated page. Note that the duration is shifted by 1 minute (60000ms) when recording the metric, because UMA cannot record negative values. If the UA starts to parse the main resource after activation, the number will be less than 60000(ms). If the UA starts to parse the main resource before activation, the number will be greater than 60000(ms). This metric will be recorded when a session ends, at PrerenderPageLoadMetricsObserver::MaybeRecordDocumentLoadMetrics. sullivan@chromium.org speed-metrics-dev@chromium.org Records the total paint area in pixels for a soft navigation. Recorded when the soft navigation context is exhausted. This metric is only recorded when the soft navigation was {Status}. sullivan@chromium.org speed-metrics-dev@chromium.org Records the total paint area as a percentage of the required paint area for a soft navigation, multiplied by 100 as "points". The multiplication is to increase precision, which will be needed in the lowest values especially. Recorded when the soft navigation context is exhausted. This metric is only recorded when the soft navigation was {Status}. iclelland@chromium.org speed-metrics-dev@chromium.org Records the outcome of the soft navigation heuristics when the page's URL is changed through the history API. This is recorded at most once for each URL change. If the URL change was not attributable to a user interaction, that is recorded immediately. If a soft navigation is detected, then it is recorded as soon as we detect it (when all conditions are satisfied). Otherwise, to be sure that all tasks associated with the user interaction have completed, we wait until all TaskAttributionInfo objects created within the SoftNavigationHeuristics::EventScope are garbage-collected, and then record which of the conditions was not satisfied. bmcquade@chromium.org skobes@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the page (including all subframes). Higher values correspond to greater instability, which is bad. Recorded at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Stable since M79; previous versions are expermental and subject to fluctuation between releases. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.LayoutInstability.CumulativeShiftScore.AfterBackForwardCacheRestore. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog hajimehoshi@chromium.org bfcache-dev@chromium.org Measures the cumulative layout shift score (bit.ly/3fQz29y) that has occurred on the page (including all subframes) after the page is restored from the back-forward cache. Recorded when the user navigates away or closes the page after the page was restored from back-forward cache. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.LayoutInstability.CumulativeShiftScore. These two histograms will be aggregated on the server to form the authoritative metric. hajimehoshi@chromium.org bfcache-dev@chromium.org Measures the cumulative layout shift score (bit.ly/3fQz29y) that has occurred in the main frame after the page is restored from the back-forward cache. Recorded when the user navigates away or closes the page after the page was restored from back-forward cache. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the cumulative layout shift score (bit.ly/lsm-explainer) that has occurred on the page (including all subframes) until the first time the page moves from the foreground to the background. It is recorded when the tab is first hidden after it is first shown in foreground. This metric is trying to record the layout shift values which are not able to be recorded in PageLoad.LayoutInstability.CumulativeShiftScore for some reasons. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in after back forward cache restore. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Replaces PageLoad.LayoutInstability.MaxCumulativeShiftScore.AfterBackForwardCacheRestore.SessionWindow.Gap1000ms.Max5000ms and increases granularity in order to get more coverage for ~5% of values in the 0-0.1 range. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. If {Bfcache} is triggered, we record the metric when the user navigates away or closes the page after the page was restored from back-forward cache. Otherwise, we record it at the end of the page lifetime, such as when the page is being navigated away from or when a tab is being closed. Replaces PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms and increases granularity to get coverage for ~25% of the values in the 0-0.1 range. lanwei@chromium.org speed-metrics-dev@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred in a Window until the first time the page moves from the foreground to the background. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 10000x the fractional cumulative layout shift score described in the explainer. It is recorded when the tab is first hidden after it is first shown in foreground. This metric is trying to record the layout shift values which are not able to be recorded in PageLoad.LayoutInstability.MaxCumulativeShiftScore.SessionWindow.Gap1000ms.Max5000ms2 for some reasons. Replaced Experimental.LayoutInstability.MaxCumulativeShiftScoreAtFirstOnHidden.SessionWindow.Gap1000ms.Max5000ms and increases granularity to get coverage for ~25% of the values in the 0-0.1 range. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the time the navigation commit request is sent to the renderer, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each HTTP or HTTPS page load. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can start before the beforeunload handler runs to b) when the (existing regular) navigation starts, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each HTTP or HTTPS page load. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the OS-level timestamp of the user input event that started a navigation to b) when the navigation starts, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each HTTP or HTTPS page load. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the time the navigation commit request is sent to the renderer to b) the time the renderer starts parsing the HTML. This is recorded for each page load. bmcquade@chromium.org iclelland@chromium.org speed-metrics-dev@chromium.org For page loads that start in the foreground, measures the duration of time until one of the following events occurs: the load of the main resource fails, the page load is stopped, the tab hosting the page is closed, the render process hosting the page goes away, a new navigation which later commits is initiated in the same tab, or the tab hosting the page is backgrounded. This metric has a very long tail, for pages that spend a long period of time in the foreground. As such, use of the mean or tail values are not recommended. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the user first foregrounds an initially backgrounded tab. Only measures navigations that started in the background. gklassen@chromium.org sullivan@chromium.org Records the state of paid content detection for the page load. The state can be kUnknown (initial value), kHasPaidContent (paid content metadata found), or kNoPaidContentFound (no paid content metadata found), based on `isAccessibleForFree` document metadata. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the first contentful paint, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each HTTP or HTTPS page load. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the largest contentful paint, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each HTTP or HTTPS page load. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from a background tab being switched to the foreground to the time the first contentful paint is performed, for main frame documents. sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The time from navigation start to first "contentful" paint. This metric does not include all page loads. Specifically, it excludes: - Page loads which have not been in the foreground during the entire loading time. Use PageLoad.PaintTiming.NavigationToFirstContentfulPaint.Background.HttpsOrDataOrFileScheme histogram if you want to include those. - Page loads for non http(s) schemes. Use PageLoad.PaintTiming.NavigationToFirstContentfulPaint.{DataScheme,FileScheme} histograms for data for page loads for data:// and file:// schemes. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.PaintTiming.NavigationToFirstPaint.AfterBackForwardCacheRestore. These two histograms will be aggregated on the server to form the authoritative metric. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The time from navigation start to first "contentful" paint, where the page was backgrounded at least once from navigation start to this event. Includes page loads with http, https, data and file schemes. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. fdoray@chromium.org catan-team@chromium.org This is recorded at the same time and with the same value as PageLoad.PaintTiming.NavigationToFirstContentfulPaint, but only if the navigation isn't a post-discard reload. anthonyvd@chromium.org catan-team@chromium.org Measures the time from navigation start to first contentful paint. This is only recorded for non-tab webUI pages, such as side-panel content. anthonyvd@chromium.org catan-team@chromium.org Measures the time from navigation start to first contentful paint for webUI. This is only recorded for webUI pages that are not blocked if users do not visit chrome://about and enable debugging pages. sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The time from navigation start to first "contentful" paint for {Scheme}. This metric does not include all page loads. If you need all page loads for http, https, data and file schemes, add PageLoad.PaintTiming.NavigationToFirstContentfulPaint.Background.HttpsOrDataOrFileScheme. Some popular WebView apps such as Gmail use data or file schemes to load their content, and having page load metrics for those apps would be useful for performance investigations. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. sullivan@chromium.org mych@chromium.org speed-metrics-dev@chromium.org The time from navigation start to first contentful paint, {NavigationScenario} This is only logged on desktop, in addition to the main PageLoad.PaintTiming.NavigationToFirstContentfulPaint histogram. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first image is painted, for main frame documents. For images that render progressively, this is recorded as soon as any image pixels have been drawn. sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the first paint is performed, for main frame documents. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org. djw@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org Measures the time from back-forward navigation timing's navigation start to the time the first paint is performed, for main frame documents. Recorded only when the page is restored from back-forward cache. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.PaintTiming.NavigationToFirstContentfulPaint. rakina@chromium.org bfcache-dev@chromium.org speed-metrics-dev@chromium.org Measures the time duration between the page restore from BFcache and the {Count} requestAnimationFrame time. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Bucketing for this histogram should be kept in sync with bucketing for PageLoad.PaintTiming.NavigationToFirstContentfulPaint. These two histograms will be aggregated on the server to form the authoritative metric. anthonyvd@chromium.org catan-team@chromium.org Measures the time from navigation start to largest contentful paint for webUI. This is only recorded for webUI pages that are not blocked if users do not visit chrome://about and enable debugging pages. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. The value is recorded at the end of each page load or the latest time when we can reliably record: when the page is navigated away, the browser is closed, or on Android when the browser is backgrounded. This metric does not include all page loads. Specifically, it excludes: - Page loads which have not been in the foreground during the entire loading time. Use PageLoad.PaintTiming.NavigationToLargestContentfulPaint2.Background.HttpsOrDataOrFileScheme histogram if you want to include those. - Page loads for non http(s) schemes. Use PageLoad.PaintTiming.NavigationToLargestContentfulPaint2.{DataScheme,FileScheme} histograms for data for page loads for data:// and file:// schemes. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog sullivan@chromium.org speed-metrics-dev@chromium.org chrome-analysis-team@google.com The time from navigation start to first "contentful" paint, where the page was backgrounded at least once from navigation start to this event. Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames, where the page was backgrounded at least once from navigation start to this event. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. The value is recorded at the end of each page load or the latest time when we can reliably record: when the page is navigated away, the browser is closed, or on Android when the browser is backgrounded. Includes page loads with http, https, data and file schemes. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. sisidovski@google.com kouhei@chromium.org Similar to PaintTiming.NavigationToLargestContentfulPaint2, this measures the time in milliseconds from navigation timing's navigation start to the time when the page first paints the largest content (text or image) in the cross-site subframe which is the top candidate of largest contentful paint. fdoray@chromium.org catan-team@chromium.org This is recorded at the same time and with the same value as PageLoad.PaintTiming.NavigationToLargestContentfulPaint2, but only if the navigation isn't a post-discard reload. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, for main frame documents. See PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 for more information. anthonyvd@chromium.org catan-team@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, for main frame documents of non-tab webUI pages, such as side-panel content. See PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 for more information. yoichio@chromium.org loading-dev@chromium.org Similar to PaintTiming.NavigationToLargestContentfulPaint2, this measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted only for pages using Speculation Rules API and calls Prerender2, across all frames. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted for {Scheme}, across all frames. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. The value is recorded at the end of each page load or the latest time when we can reliably record: when the page is navigated away, the browser is closed, or on Android when the browser is backgrounded. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog lanwei@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames. Recorded at the point when a page which has been opened in the foreground is moved to the background for the first time. Excludes any content painted after user input. Includes content that has been removed from the page. See web.dev/lcp for more details. This metric is trying to record the LCP values which are not able to be recorded in PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 for some reasons. Do not modify this metric in any way without contacting speed-metrics-dev@chromium.org AND chrome-analysis-team@google.com. Log of major changes: http://bit.ly/chrome-speed-metrics-changelog mych@chromium.org iclelland@chromium.org sullivan@chromium.org speed-metrics-dev@chromium.org Measures the time from navigation timing's navigation start to the time the largest content (text or image) is first painted, across all frames, {NavigationScenario} This is only logged on desktop, in addition to the main PageLoad.PaintTiming.NavigationToLargestContentfulPaint2 histogram. bmcquade@chromium.org csharrison@chromium.org speed-metrics-dev@chromium.org Measures the time from when the HTML parser started, to when the page first paints content. chikamune@chromium.org chrome-loading@google.com Measures the duration from the time the renderer starts parsing the HTML to the time the largest contentful paint occurs. This is recorded for each page load. chikamune@chromium.org chrome-loading@google.com Measures the duration from a) the "actual" navigation starts which can begin before beforeunload handlers run to b) the time the parser started, excluding the time spent waiting for user interaction in beforeunload dialogs. This includes the time spent running beforeunload JavaScript handlers. This is recorded for each HTTP or HTTPS page load. bmcquade@chromium.org csharrison@chromium.org Measures the time from navigation timing's navigation start to the time the parser started, for main frame documents. sullivan@chromium.org iclelland@chromium.org haoliuk@chromium.org Measures the maximum cumulative layout shift (bit.ly/cls-explainer) that has occurred from the time when the soft navigation happens to the time when the next soft navigation happens or the page load ends in a session window. The gap between two consecutive shifts in a window is not bigger than 1000ms and the maximum window size is 5000ms. This metric's integral value is 100x the fractional cumulative layout shift score described in the explainer. sullivan@chromium.org iclelland@chromium.org haoliuk@chromium.org An approximation of a high percentile of user interaction latency from the time when the soft navigation happens to the time when the next soft navigation happens or the page load end, in ms. For this metric, we measure the latency of user interactions as described here: https://web.dev/inp sullivan@chromium.org iclelland@chromium.org haoliuk@chromium.org Measures the LargestContentfulPaint in milliseconds from the start time of the soft navigation to the LCP time. sullivan@chromium.org johannes@chromium.org speed-metrics-dev@chromium.org Reports the state in which the SoftNavigationPageLoadMetricsObserver is when an OnSoftNavigation event arrives. sullivan@chromium.org johannes@chromium.org speed-metrics-dev@chromium.org Measures the start time of the soft navigation in milliseconds from the start of the hard navigation. jkarlin@chromium.org chrome-analysis-team@google.com Records the time from frame navigation start to FirstContentfulPaint of each ad frame that receives a FirstContentfulPaint. The time could be quite large, as some ads don't paint until they're scrolled into view. But the metric is still useful in aggregate. Recorded for all ad frames with non-zero bytes or cpu usage that receive a FirstContentfulPaint. Recorded when the ad frame or page is destroyed. Changes to how cross-origin content is loaded (e.g., security policies, network prioritization) or to iframes can certainly affect this metric. {AdsPageLoadMetricVisibilityType} Do not modify this metric in any way without contacting chrome-analysis-team@google.com. jkarlin@chromium.org alexmt@chromium.org Records the time from top frame navigation start to FirstContentfulPaint of each ad frame that receives a FirstContentfulPaint. The time could be quite large, as some ads don't paint until they're scrolled into view. But the metric is still useful in aggregate. Recorded for all ad frames with non-zero bytes or cpu usage that receive a FirstContentfulPaint. Recorded when the ad frame or page is destroyed. Changes to how cross-origin content is loaded (e.g., security policies, network prioritization) or to iframes can certainly affect this metric. {AdsPageLoadMetricVisibilityType} jkarlin@chromium.org alexmt@chromium.org chrome-ads-histograms@google.com Only recorded if the page has at least one identified ad frame. Recorded in PageLoadMetrics when the page is destroyed. Bytes include all bytes used by the network to load a resource and response body bytes for cached resources (from both the HTTP and memory caches). An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Includes resources that did not finish loading. {AdsPageLoadMetricVisibilityType} jkarlin@chromium.org chrome-ads-histograms@google.com Only recorded if the page has at least one identified ad frame. Recorded in PageLoadMetrics when the page is destroyed. Cpu measures the wall time of tasks attributable to a frame as reported by the MainThreadTaskScheduler as well as time spent servicing scripted animations by each document (not attributable by the MainThreadTaskScheduler). An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Includes resources that did not finish loading. Does not consider time while a page is backgrounded. {AdsPageLoadMetricVisibilityType} Warning: This metric expired around 04/2022 and was unexpired 07/2023. Data may be missing. jkarlin@chromium.org chrome-ads-histograms@google.com For each identified ad frame, whether the origin of the ad matches the origin of the main frame, differs from the origin of the main frame, or is indeterminable. An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Frames of zero bytes (e.g., never had a document or their document was doc.written and no sub-resources were loaded) are not counted. {AdsPageLoadMetricVisibilityType} Warning: This metric expired around 04/2022 and unexpired 07/2023. Data may be missing. csharrison@chromium.org chrome-ads-histograms@google.com For each identified ad frame, whether the sticky user activation bit was ever set on the frame. Recorded for each ad frame when the page is destroyed or navigated away from, including ad frames that no longer exist. An ad frame consists of the identified ad frame and all of its children (which may also be ads, but are counted as part of the ancestor ad frame). Frames of zero bytes (e.g., never had a document or their document was doc.written and no sub-resources were loaded) are not counted. {AdsPageLoadMetricVisibilityType} Warning: this histogram was expired from 2024-04-17 until 2025-05-27; data may be missing. jkarlin@chromium.org chrome-ads-histograms@google.com The number of frames on the page that have loaded more than 0 bytes of content or had non-zero CPU usage. For pages with zero ad frames, the other PageLoad.Clients.Ads metrics are not recorded unless otherwise specified. This metric is not recorded on sites where the subresource filter is enabled. Child frames of an ad frame are not included in the count. {AdsPageLoadMetricVisibilityType} jkarlin@chromium.org chrome-ads-histograms@google.com Records heavy ad type for each ad frame, as determined by the first threshold hit (see FrameData::HeavyadStatus). This is recorded regardless of feature flag or other conditions that prevent the heavy ad intervention from occurring. This includes 1 megabyte of random additive noise on the network threshold. As such, it is possible for this histogram to record different values for the same frame than PageLoad.HeavyAds.ComputedType2. Recorded for all ad frames with non-zero bytes. Recorded when the ad frame destroyed or when the page is destroyed. It is possible for multiple thresholds to be hit at the same time, with the higher valued enums winning those race conditions. {AdsPageLoadMetricVisibilityType} Warning: this histogram was expired from 2024-04-17 until 2025-05-27; data may be missing. jkarlin@chromium.org chrome-ads-histograms@google.com Records the type of heavy ad unloaded by the heavy ad intervention. Heavy ad type is determined by the first threshold hit. This is not recorded for ad frames that are considered heavy but did not fulfill other criteria for the intervention. This includes the feature being enabled and being below the per-origin intervention cap. It is possible for multiple thresholds to be hit at the same time, with the higher valued enums winning those race conditions. {AdsPageLoadMetricVisibilityType} Warning: this histogram was expired from 2024-04-17 until 2025-05-27; data may be missing. harringtond@chromium.org offline-dev@chromium.org Reports whether a resource fetch was successful while saving a page to MHTML. Reported for each resource fetched. harringtond@chromium.org offline-dev@chromium.org Reports the time taken to serialize a single frame of an MHTML file. Includes only time taken by frame_serializer.cc. Reported when frame serialization completes.