Cr is a tool that tries to hide some of the tools used for working on Chromium behind an abstraction layer. Nothing that cr does can't be done manually, but cr attempts to make things nicer. Its main additional feature is that it allows you to build many configurations and run targets within a single checkout (by not relying on a directory called ‘out’). This is especially important when you want to cross-compile (for instance, building Android from Linux or building arm from intel), but it extends to any build variation.

A quick example

The following is all you need to prepare an output directory, and then build and run the release build of chrome for the host platform:

cr init
cr run

How do I get it?

You already have it, it lives in src/tools/cr

You can run the file by hand, but if you are using bash it is much easier to source the bash helpers. This will add a cr function to your bash shell that runs with pyc generation turned off, and also installs the bash tab completion handler (which is very primitive at the moment, it only completes the command not the options) It also adds a function you can use in your prompt to tell you your selected build (_cr_ps1), and an helper to return you to the root of your active tree (crcd). I recommend you add the following lines to the end of your ~/.bashrc (with a more correct path):

source ${CR_CLIENT_PATH}/src/tools/cr/

At that point the cr command is available to you.

How do I use it?

It should be mostly self documenting

cr --help

will list all the commands installed

cr --help command

will give you more detailed help for a specific command.

A note to existing Android developers:

  • Do not source envsetup! ever!
  • If you use cr in a shell that has had envsetup sourced, miscellaneous things will be broken. The cr tool does all the work that envsetup used to do in a way that does not pollute your current shell.
  • If you really need a shell that has had the environment modified like envsetup used to do, see the cr shell command, also probably file a bug for a missing cr feature!

The commands

Below are some common workflows, but first there is a quick overview of the commands currently in the system.

Output directory commands


Create and configure an output directory. Also runs select to make it the default.


Select an output directory. This makes it the default output for all commands, so you can omit the --out option if you want to.


Prepares an output directory. This runs any preparation steps needed for an output directory to be viable, which at the moment means run gyp.

Build commands


Build a target.


Install a binary. Does build first unless --builder==skip. This does nothing on Linux, and installs the apk onto the device for Android builds.


Invoke a target. Does an install first, unless --installer=skip.


Debug a target. Does a run first, unless --runner=skip. Uses the debugger specified by --debugger.

Other commands


Sync the source tree. Uses gclient sync to do the real work.


Run an exernal command in a cr environment. This is an escape hatch, if passed a command it runs it in the correct environment for the current output directory, otherwise it starts a sub shell with that environment. This allows you to run any commands that don't have shims, or are too specialized to get one. This is especially important on Android where the environment is heavily modified.

Preparing to build

The first thing you need to do is prepare an output directory to build into. You do this with:

cr init

By default on Linux this will prepare a Linux x86 release build output directory, called out_linux/Release, if you want an Android debug one, you can use:

cr init --out=out_android/Debug

The output directory can be called anything you like, but if you pick a non standard name cr might not be able to infer the platform, in which case you need to specify it. The second part must be either Release or Debug. All options can be shortened to the shortest non ambiguous prefix, so the short command line to prepare an Android debug output directory in out is:

cr init --o=out/Debug --p=android

It is totally safe to do this in an existing output directory, and is an easy way to migrate an existing output directory to use in cr if you don't want to start from scratch.

Most commands in cr take a --out parameter to tell them which output directory you want to operate on, but it will default to the last value passed to init or select. This enables you to omit it from most commands.

Both init and select do additional work to prepare the output directory, which include things like running gyp. You can do that work on it's own with the prepare command if you want, something you need to do when changing between branches where you have modified the build files.

If you want to set custom GYP defines for your build you can do this by adding adding the -s GYP_DEFINES argument, for example:

cr init --o=out/Debug -s GYP_DEFINES=component=shared_library

Running chrome

If you just want to do a basic build and run, then you do

cr run

which will build, install if necessary, and run chrome, with some default args to open on The same command line will work for any supported platform and mode. If you want to just run it again, you can turn off the build and install steps,

cr run --installer=skip

note that turning off install automatically turns off build (which you could do with --builder=skip) as there is no point building if you are not going to install.

Debugging chrome

To start chrome under a debugger you use

cr debug

which will build, install, and run chrome, and attach a debugger to it. This works on any supported platform, and if multiple debuggers are available, you can select which one you want with --debugger=my_debugger

Help, it went wrong!

There are a few things to do, and you should probably do all of them. Run your commands with dry-run and/or verbose turned on to see what the tool is really doing, for instance

cr --d -vvvv init

The number of v‘s matter, it’s the verbosity level, you can also just specify the value with -v=4 if you would rather.

Report a bug, even if it is just something that confused or annoyed rather than broke, we want this tool to be very low friction for developers.

Known issues

You can see the full list of issues with this query, but here are the high level issues:

  • Only supports gtest : You run tests using the run command, which tries to infer from the target whether it is a runnable binary or a test. The inference could be improved, and it needs to handle the other test types as well.
  • No support for Windows or Mac : allowed for in the design, but need people with expertise on those platforms to help out
  • Bash completion : The hooks for it are there, but at the moment it only ever completes the command, not any of the arguments