# Largest Contentful Paint Changes in Chrome 133

## Expose coarsened cross-origin renderTime in element timing/LCP (regardless of TAO)

Prior this change all cross-origin element-timing and LCP performance entries
would have a zero renderTime, unless they were served with the appropriate
Timing-Allow-Origin HTTP header to allow access to detailed timings. Without a
renderTime LCP falls back ot the load time for LCP which can often be well
before the load time. This can result in anomalies such as LCP appearing to
happen before FCP, which is of course not possible.

With this change presentation timestamps (renderTime, paint timing start time,
event timing end time) are instead just coarsened to a 4ms multiple to mitigate
the risk of reading cross-origin image information.

For more details see the [Chrome Status entry](https://chromestatus.com/feature/5128261284397056)

### How does this affect a site's metrics?

User may notice an increased LCP time in Real User Monitoring (RUM) metrics.
The issue did not affect the Chrome User Experience Report (CrUX), and this was
one example of [differences between CrUX and RUM](https://web.dev/articles/crux-and-rum-differences#cross-origin_resources).

The LCP is now more accurate and more in line with CrUX so this is not a
performance regression, but more an improvement to measurements of LCP.

### When were users affected?

Launch was the week of Feb 27, 2025, when m133 was in stable, but a limited
number of early adopters might have seen this change as early as m132.