--- breadcrumbs: - - /chromium-os/developer-library/guides - ChromiumOS > Guides page_name: debug-buttons title: Debug Button Shortcuts --- ChromeOS devices provide a variety of advanced keyboard and button shortcuts that are useful for debugging. We document those here, as well as highlight some differences between devices with and without keyboards. [TOC] ## Devices With Keyboards See the [official support page] for non-debug keyboard shortcuts. Note that some of the below debug keyboard shortcuts are implemented at a very low level and are not keyboard-layout aware. When in doubt, assume debug shortcuts refer to the physical mapping of a US keyboard layout. Shortcuts with an asterisk (**\***) also work with tablets/detachables with a keyboard attached. Functionality | Shortcut ------------------------------------- | -------- Clean shutdown | Power button, hold for 3 - 8 seconds Hard shutdown | Power button, hold for 8 seconds Screenshot capture | `Ctrl + Switch-Window` **\*** File feedback / bug report | `Alt + Shift + I` **\*** Powerwash | `Ctrl + Alt + Shift + R` from login screen **\*** Full system reset | `Power + Refresh + ChromeOS-Back (F1)`, hold for 10 seconds. Only works on some models starting in 2023. EC reset | `Power + Refresh` Recovery mode | See [firmware keyboard UI] section Developer mode | See [firmware keyboard UI] section Battery cutoff (newer devices) | Press and hold the `Refresh` key, and tap `Power`. Then, while holding `Refresh`, disconnect the power adapter cord for 5 seconds. Battery cutoff (older* devices) | While pressing the `Power + Refresh` keys, disconnect the power adapter cord for 5 seconds. Warm AP reset | `Alt + Volume-Up + R` Restart Chrome | `Alt + Volume-Up + X` **\*** Kernel panic/reboot | `Alt + Volume-Up + X + X` **\*** Reboot EC but don't boot AP | `Alt + Volume-Up + Down-Arrow` Force EC hibernate | `Alt + Volume-Up + H` Override USB-C port used for charging | `Left-Ctrl + Right-Ctrl + Search + (0 or 1 or 2)` **\*** Virtual terminal switching | `Ctrl + Alt + F1 (or F2, F3, F4)` **\*** *Notes:* * AP = Application Processor; EC = Embedded Controller. *  EC hibernate is supported only on devices with select Embedded Controllers. * `Alt + Volume-Up` is treated as the [Magic SysRq] key. When in Developer mode, you can enable SysRq key combinations as documented in the Linux kernel docs. * Overriding the charging port is only supported on Samus. * **Older** devices (see Battery cutoff) can be identified by the lack of the `G` (Google) key in the keyboard bottom-row. ### Firmware Keyboard Interface * **Recovery mode**: Hold `Esc + Refresh` ![][refresh-icon] and press `Power`. * On some Chromebooks the combination to hold is `Esc + Full screen` ![][fullscreen-icon] instead. * From here, follow the instructions at https://google.com/chromeos/recovery to recover your device using external media. * **Recovery mode**: Engage the small `Reset` pinhole with a paperclip, hit `Power` and continue engaging `Reset` for 2 seconds. Typically (only?) for chromeboxes with a QWERTY keyboard attached. * From here, follow the instructions at https://google.com/chromeos/recovery to recover your device using external media. * **Developer mode**: To enter [Developer Mode], first enter recovery mode, then press `Ctrl + D`, followed by `Enter` to accept. * Note that [Developer Mode] disables security features and may leave your device open to attack. Only enable if you understand the risks. * Devices in [Developer Mode] will show a warning screen on every boot. The screen will time out after 30 seconds, playing a warning beep. * From the warning screen, the following keyboard shortcuts are available: * `Ctrl + D`: Boot the system from the internal disk. * `Ctrl + U`: Boot the system from an external USB stick or SD card. The option `crossystem dev_boot_usb=1` must be set from the command line before this option is available. * `Ctrl + L`: Chain-load an alternative bootloader (e.g. SeaBIOS). This may allow booting other Operating Systems more easily. Not all devices are shipped with alternative bootloaders. New alternative bootloaders can be manually installed on the device from [Developer Mode]. The option `crossystem dev_boot_legacy=1` must be set from the command line before this option is available. * `0` through `9`: On newer (2019+) platforms, more than one alternative bootloader can be installed and `Ctrl + L` will show a selection menu. On these devices, the number keys can be used to directly boot the numbered bootloader without going through the menu. * The option `crossystem dev_default_boot=usb` can be set to override the default boot behavior if no key combination is pressed for 30 seconds. [refresh-icon]: https://lh3.googleusercontent.com/3XKnstOuiq5G1zw_fiVWq18N1Q5nBcmrj9-Yqq5hYeFnD7XkMAWpAwBo12CpF098UJc=w36-h36 [fullscreen-icon]: https://storage.googleapis.com/support-kms-prod/ZgwI1JWIMPXn0bOjJXIbIkYraiD8KtwGrJRH Some devices do not support `Esc + Power + Refresh` for entering Recovery Mode: * Chromeboxes have a recovery button. To enter Recovery Mode, hold down the recovery button and press `Power`. * To enter [Developer Mode] on a Chromebox, first enter recovery mode and press `Ctrl + D` on the keyboard, then push the physical recovery button on the Chromebox to accept. * Older devices have a physical [Developer Mode] switch. You can read up on your particular device under the [device-specific developer information] table. _Note_: An additional, deeper reset (with forced memory retraining) can be triggered on some devices on the way to recovery mode by holding `Left-Shift` during the normal recovery sequence (i.e., `Left-Shift + Esc + Refresh + Power`). ## Devices Without Keyboards ### Shortcuts Starting in 2018, keyboardless ChromeOS devices are being built, in tablet and detachable form factors. Without a keyboard, some typical keyboard-based debugging shortcuts can't be supported. Below are the shortcuts for performing various system and debugging tasks with only the limited physical buttons and touch screen found on tablets or detachable devices. Note that some of the following behaviors work on [convertible] devices when used in tablet mode. Note: If the tablet has a detachable keyboard, remember to detach it before trying these shortcuts. Functionality | Shortcut ------------------- | ---------------------------------------------------------- Screen off | Power button, short press Clean shutdown | Power button, hold for 3 seconds, select option in menu Hard shutdown | Power button, hold for 10 seconds Screenshot capture | `Power + Volume-Down`, short press File feedback | Power button, hold for 3 seconds, select option in menu EC reset | `Power + Volume-Up`, hold for 10 seconds Recovery mode | See [firmware menu UI] section Developer mode | See [firmware menu UI] section Battery cutoff | `Power + Volume-Up`, hold for 10 seconds, disconnect the power adapter cord Warm AP reset | See [EC debug mode] section Restart Chrome | See [EC debug mode] section Kernel panic/reboot | See [EC debug mode] section *Notes:* * Filing feedback from the power button menu is currently (as of 2018-10-19) only [supported](https://crbug.com/845558#c8) on canary (for all users) and dev/beta/stable (for Google employees) release channels. All users can still file feedback via the browser options menu (`Help > Report an issue...`). * Battery cutoff shortcut is supported only on devices with a [smart battery] (e.g., not Scarlet, Dru). ### Firmware Menu Interface The [boot firmware screen] is accessible through keyboard shortcuts on devices with keyboards; on keyboardless devices, the following methods are supported: * **Recovery mode**: `Power + Volume-Up + Volume-Down`, hold for 10 seconds. If the screen turns off or on during that period, ignore it and make sure you keep all three buttons held down for the whole 10 second period, then release them. * From here, follow the instructions at https://google.com/chromeos/recovery to recover your device using external media. * To change the UI language or display additional debugging information, you can press either `Volume-Up` or `Volume-Down`. This leads to a menu that can be navigated with the volume buttons, and menu items can be selected with the power button. * **Developer mode**: Enter recovery mode and press `Volume-Up + Volume-Down` simultaneously, then select "Confirm Enabling Developer Mode" in the menu. * Note that [Developer Mode] disables security features and may leave your device open to attack. Only enable if you understand the risks. * Devices in [Developer Mode] display a similar menu on every boot that allows selecting developer boot options. The menu will time out and boot after no key has been pressed for 30 seconds, playing a warning beep. * The "USB or SD card" and "Legacy BIOS" boot menu options need to be enabled on the command line before they work, same as with the [firmware keyboard UI]. * In addition to selecting boot options in the menu, the following shortcut combinations are available in the developer warning menu: * Press `Volume-Down` for 3+ seconds, then release: Boot the system from the internal disk. * Press `Volume-Up` for 3+ seconds, then release: Boot the system from an external USB stick or SD card. * If a keyboard is connected, all boot shortcuts from the [firmware keyboard UI] are also available in the developer warning menu. _Note_: An additional, deeper reset (with forced memory retraining) can be triggered on some devices on the way to recovery mode by holding `Power + Volume-Up + Volume-Down` for 30 seconds (until the LED starts flashing). ### EC Debug Mode Not all debugging shortcuts are implemented with a simple combination of buttons—some are found by utilizing multi-button sequences, initiated after entering a special EC state called "debug mode". To enter debug mode, press `Volume-Up + Volume-Down` for 10 seconds. Release once the charging LED starts flashing. Once in debug mode, any of the following actions can be taken, using `Volume-Up` (`U`) and `Volume-Down` (`D`) buttons. Supported codes: Functionality | Sequence ------------------ | -------- Restart Chrome | `UD` Kernel panic/crash | `UUD` Warm reset | `DU` Debug mode is cancelled when a sequence finishes, or after 10 seconds without a volume button press. ## Firmware Log Viewer For boards launched after Oct 2020 (such as puff, zork, volteer), the firmware menu UI supports viewing debug info/firmware logs (by selecting "Advanced options" then "Debug info"/"Firmware log"). Navigation is as easy as selecting "Page up", "Page down" buttons from the menu. For boards launched after Nov 2023 (such as rex, geralt), the text area in the log viewer is enlarged, and the screen becomes menu-less (see the screenshot below). ![Firmware log viewer](https://storage.googleapis.com/chromium-website-lob-storage/74207681de753053172f723f3c793183c3f29cd8) The following on-device buttons and keyboard shortcuts are supported for navigation. Functionality | Shortcut for Devices With Keyboards | Shortcut for Devices Without Keyboards ------------------- | ----------------------------------- | -------------------------------------- Page up | `Up-Arrow` | `Volume-Up` Page down | `Down-Arrow` | `Volume-Down` Back | `Enter` | Power button, short press First page | `Left-Arrow` Last page | `Right-Arrow` Previous boot stage | `Ctrl + Z` Next boot stage | `Ctrl + X` [official support page]: https://support.google.com/chromebook/answer/183101 [firmware keyboard UI]: #firmware-keyboard-interface [Magic SysRq]: https://www.kernel.org/doc/html/latest/admin-guide/sysrq.html [Developer Mode]: /chromium-os/developer-library/guides/device/developer-mode/ [convertible]: https://en.wikipedia.org/wiki/Laptop#Convertible [firmware menu UI]: #firmware-menu-interface [EC debug mode]: #ec-debug-mode [smart battery]: http://sbs-forum.org/specs/sbdat110.pdf [device-specific developer information]: /chromium-os/developer-library/reference/development/developer-information-for-chrome-os-devices [boot firmware screen]: /chromium-os/developer-library/guides/device/developer-mode/