Code of Conduct

We follow the Chromium code of conduct in our our repos and organizations, mailing lists, and other communications.


Install [depot_tools] (

Then checkout the catapult repo.

git clone

You can then create a local branch, make and commit your change.

cd catapult
git checkout -t -b foo origin/master
... edit files ...
git commit -a -m "New files"

Once you're ready for a review do:

git cl upload

Once uploaded you can view the CL in Rietveld and request a review by clicking the ‘publish & mail’ link. You can also click the “CQ Dry Run” link to run all the tests on your change.

If you get review feedback, edit and commit locally and then do another upload with the new files. Before you commit you‘ll want to sync to the tip-of-tree. You can either merge or rebase, it’s up to you.

Then, submit your changes through the commit queue by checking the “Commit” box.

Once everything is landed, you can cleanup your branch.

git checkout master
git branch -D foo


If you're new to the chromium-family of projects, you will also need to sign the chrome contributors license agreement. You can sign the [Contributor License Agreement] (, which you can do online. It only takes a minute. If you are contributing on behalf of a corporation, you must fill out the [Corporate Contributor License Agreement] ( and send it to us as described on that page.

If you‘ve never submitted code before, you must add your (or your organization’s) name and contact info to the Chromium AUTHORS file.

Contributing from a Chromium checkout

If you already have catapult checked out as part of a Chromium checkout and want to edit it in place (instead of having a separate clone of the repository), you will probably want to disconnect it from gclient at this point so that it doesn't do strange things on updating. This is done by editing the .gclient file for your Chromium checkout and adding the following lines:

'custom_deps': {
    'src/third_party/catapult': None,

In order to be able to land patches, you will most likely need to update the origin remote in your catapult checkout to point directly to this GitHub repository. You can do this by executing the following command inside the catapult folder (third_party/catapult):

git remote set-url origin

Code style

We follow the [Chromium style] (

If you're contributing to Trace Viewer, refer to the Trace Viewer style guide.

Individual project documentation

Look to individual project documentation for more info on getting started:


Check individual project documentation for instructions on how to run tests. You can also check the current status of our tests on the waterfall. Use the “commit” checkbox in rietveld to commit through the commit queue, which automatically runs all tests. Run the tests before committing with the “CQ dry run” link.

Updating Chromium's about:tracing (rolling DEPS)

Chromium‘s DEPS file needs to be rolled to the catapult revision containing your change in order for it to appear in Chrome’s about:tracing or other third_party/catapult files. This should happen automatically, but you may need to do it manually in rare cases. See below for more details.

Automatic rolls

DEPS should be automatically rolled by the auto-roll bot at will be cc-ed on all reviews, and anyone who wants to join that list can subscribe. It's also the correct list to report a problem with the autoroll. If you need to stop the autoroll, either sign into that page with a account, or contact

Manual rolls

In rare cases, you may need to make changes to chromium at the same time as you roll catapult DEPs. In this case you would need to do a manual roll. Here are instructions for rolling catapult DEPS, your CL would also include any other changes to chromium needed to complete the roll.

First, commit to catapult. Then check the [mirror] ( to find the git hash of your commit. (Note: it may take a few minutes to be mirrored).

Then edit Chrome's [src/DEPS] ( file. Look for a line like:

    Var('chromium_git') + '/external/' + '@' +

Update the number to the git hash you want to roll to, and contribute a codereview to chrome for your edit. If you are a Chromium committer, feel free to TBR this.

Adding contributors

Admins (nduca, sullivan) can add contributors to the project. There are two steps:

  1. Add the person's github account to the [catapult] ( team.
  2. Add the person's email to the [commit queue list] (

Because there is no API to retrieve a person's GitHub ID from their email address or vice versa, we cannot automate this into one step.