Cross-compiling Chrome/win

As many Chromium developers are on Linux/Mac, cross-compiling Chromium for Windows targets facilitates development for Windows targets on non-Windows machines.

It‘s possible to build most parts of the codebase on a Linux or Mac host while targeting Windows. It’s also possible to run the locally-built binaries on swarming. This document describes how to set that up, and current restrictions.


What does not work:

  • 64-bit renderer processes don't use V8 snapshots, slowing down their startup (bug)
  • on Mac hosts, 32-bit builds don't use V8 snapshots either (bug has more information, but this is unlikely to ever change)

All other targets build fine (including chrome, browser_tests, ...).

Uses of .asm files have been stubbed out. As a result, Crashpad cannot report crashes, and NaCl defaults to disabled and cannot be enabled in cross builds (.asm bug).

.gclient setup

  1. Tell gclient that you need Windows build dependencies by adding target_os = ['win'] to the end of your .gclient. (If you already have a target_os line in there, just add 'win' to the list.) e.g.

    solutions = [
    target_os = ['android', 'win']
  2. gclient sync, follow instructions on screen.

If you're at Google, this will automatically download the Windows SDK for you. If this fails with an error:

Please follow the instructions at

then you may need to re-authenticate via:

cd path/to/chrome/src
# Follow instructions, enter 0 as project id.
download_from_google_storage --config

If you are not at Google, you can package your Windows SDK installation into a zip file by running the following on a Windows machine:

cd path/to/depot_tools/win_toolchain
# customize the Windows SDK version numbers
python 2017 -w 10.0.17134.0

These commands create a zip file named <hash value>.zip. Then, to use the generated file in a Linux or Mac host, the following environment variables need to be set:

export DEPOT_TOOLS_WIN_TOOLCHAIN_BASE_URL=<path/to/sdk/zip/file>
export GYP_MSVS_HASH_<toolchain hash>=<hash value>

<toolchain hash> is hardcoded in src/build/ and can be found by setting DEPOT_TOOLS_WIN_TOOLCHAIN_BASE_URL and running gclient sync:

gclient sync
Running hooks:  17% (11/64) win_toolchain
________ running '/usr/bin/python src/build/ update --force' in <chromium dir>
Windows toolchain out of date or doesn't exist, updating (Pro)...
desired_hash: <toolchain hash>

GN setup

Add target_os = "win" to your Then just build, e.g.

ninja -C out/gnwin base_unittests.exe


For now, one needs to use the rbe backend, not the (default) borg backend: login ensure_start

Copying and running chrome

A convenient way to copy chrome over to a Windows box is to build the mini_installer target. Then, copy just mini_installer.exe over to the Windows box and run it to install the chrome you just built.

Note that the mini_installer doesn't include PDB files. PDB files are needed to correctly symbolize stack traces (or if you want to attach a debugger).

Running tests on swarming

You can run the Windows binaries you built on swarming, like so:

tools/ -C out/gnwin -t base_unittests [ --gtest_filter=... ]

See the contents of for how to do this manually.

The linux-win_cross-rel buildbot does 64-bit release cross builds, and also runs tests. You can look at it to get an idea of which tests pass in the cross build.