What are watchlists?

A watchlist is a mechanism that allows a developer (a “watcher”) to watch over portions of code that the watcher is interested in. A watcher will be cc-ed on changes that modify that portion of code, thereby giving that watcher an opportunity to make comments on chromium-review.googlesource.com even before the change is committed.

Important : As watchlists are processed locally when uploading using git cl upload it is not possible to define watchlists for Gerrit CLs generated by tools such as the Skia autoroller (see crbug.com/982198). In order to be notified of autoroller commits, find the corresponding config file and add email addresses of people to be notified of roller commits in the sheriff field of the autoroller config.


Watchlists are defined using a WATCHLISTS file, which resides at the root of a repository. A typical WATCHLISTS file looks like:

    'valgrind': {
      'filepath': 'tools/valgrind/',
    'mac': {
      'filepath': 'cocoa|\.mm$|(_mac|_posix)\.(cc|h)$',
    'valgrind': ['nirnimesh@chromium.org', 'dank@chromium.org'],

In this case, watchlists named valgrind and mac are defined in WATCHLIST_DEFINITIONS and their corresponding watchers declared in WATCHLISTS.

In the example above, whenever a new changeset is created that refers to any file in tools/valgrind/, the 'valgrind' watchlist will be triggered and nirnimesh@chromium.org & dank@chromium.org will be cc-ed to the changeset for review. A regular expression can be used as the matching pattern. Matches are determined using python's re.search() function call, so matching A_WORD is the same as matching .*A_WORD.*.

Each name in WATCHLISTS must be defined first in WATCHLIST_DEFINITIONS.

Watchlist processing takes place during git-cl upload and are non-binding; that is, an approval from that watcher is not needed for commit. It merely gives the watcher an opportunity to make comments, if any.

Editing Watchlists

You create new watchlists or add yourself to existing watchlists by editing the WATCHLISTS file at the base of the repository.

It's advisable to run watchlists.py to verify that your new rules work.

Example (from src):

python third_party/depot_tools/watchlists.py PATH/TO/FILE1 PATH/TO/FILE2 ....


To override watchlist processing, use git cl upload with --bypass-hooks.