ellyjones@ / avi@
This document outlines the process by which flags in Chromium expire and are removed from the codebase. This document only describes entries in
chrome://flags, not command-line switches (commonly also called command-line flags). This process does not cover command-line switches and there continue to be no guarantees about those.
See also Chromium Flag Ownership.
If you are a user or administrator of Chrome and are using (or think you need to use) a flag to configure Chromium for your use case, please file a bug or email flags-dev@, because that flag will likely be removed at some point. If you are a Chromium developer, please carry on using flags as normal :)
Flags have never been a supported configuration surface in Chromium, and we have never guaranteed that any specific flag will behave consistently or even continue to exist. This document describes a process for removing flags that have been around for long enough that users might have come to rely on their ongoing existence in a way that hopefully minimizes pain, but Chromium developers are free to change the behavior of or remove flags at any time. In particular, just because a flag will expire through this process does not mean a developer will not remove it earlier than this process specifies.
The logic in
//tools/flags/generate_unexpire_flags.py implements most of this. At any given time, if the current value of
$MSTONE, the two previous milestones (
$MSTONE-2) are considered recent.
$MSTONEor higher are not expired
$MSTONE-3or lower are unconditionally expired
$MSTONE-2are expired by default, but can be temporarily unexpired via flags named “
There are other elements of this process not described here, such as emails to flags-dev@ tracking the status of the process.
If a flag is no longer used (for instance, it was used to control a feature that has since launched), the flag should be removed. Delete the entry in
//ios/chrome/browser/flags/about_flags.mm for iOS (and any corresponding entries for the flag description), and remove any references in
https://crbug.com/953690 is the never-to-be-closed bug to track flags that are removed.