- Edited
Post updated 18 Jul 2024. This post is directed towards community members who are assisting people with flashing GrapheneOS using the WebUSB installer from Windows, and towards people who are searching the forum for this issue.
Issue
I am using Windows 10/11, and am connecting the device to the computer while booted into the bootloader interface, and I am following the WebUSB install guide. The browser – that is officially supported by the installer – recognizes the device, and allows me to unlock the bootloader and to start flashing the release. But when the WebUSB installer reboots the device into fastbootd, the device is simply stuck in fastbootd, and the installer merely says "Restarting device" without any progress being made – even after waiting for a long while. I have checked the cable connection, tried different cables, rebooted my PC, etc. I've even tried three different Windows PCs, with the same result. The computers have sufficiently free disk space.
Solution
Windows is missing the driver for the Android Bootloader Interface, and you have to install it. The way to do this is to follow this install step, but if you need more details on how to do this, here they are:
While the device is booted into the bootloader interface: open Windows Updates, do a manual check for updates, wait for the update check to finish. Then go to Optional updates, select the update that contains "Android" within its name (might start with "Lemobile"), install it and retry the "Flash release" step of the installer.
On Windows 11, the procedure to access "Optional updates" is to first select "Advanced options" within Windows Updates.
More details
Previously, browsers on Windows were not able to recognize a device that was booted into the bootloader interface if the bootloader interface driver was not installed. But currently (checked on July 2024), with an up-to-date Windows install, browsers are able to recognize and connect to the device, and the user can unlock the bootloader and even start flashing, without the driver being installed.
I have confirmed this by using clean installs of Windows 10 and 11 (patched with the latest OS updates), connecting a Pixel device booted into the bootloader interface, then using the WebUSB installer to start flashing without installing the driver. (Here is a screen recording of this).
Why this wall of text, fid02?
It seems that the new Windows behaviour of being able to start flashing without the fastboot driver has understandably caused some confusion among community members who are assisting with install issues, but who are unaware of the new Windows behaviour. If the WebUSB installer has started flashing, that previously implied that the fastboot driver was already installed. Then, if the flashing got stuck at fastbootd, the natural next steps were to check the cable connection, trying different cables, etc. But now, being stuck at fastbootd when flashing from Windows could imply a missing fastboot driver.
Emphasis: if the flashing has proceeded past the fastbootd screen, the fastboot driver is very likely already installed.
However, you can check whether or not the driver is installed by connecting the device to the computer while in the bootloader interface and then opening Device Manager. If Windows Updates has installed the driver, it will be visible within Device Manager – the entry might be called "LeMobile Android Device" with the sub-entry "Android Bootloader Interface" (screenshot).
