Checking out and building Chromium for Android

There are instructions for other platforms linked from theget the code page.

Instructions for Google Employees

Are you a Google employee? Seego/building-android-chrome instead.

System requirements

• An x86-64 machine running Linux with at least 8GB of RAM. More than 16GB is highly recommended.
• At least 100GB of free disk space.
• You must have Git and Python installed already.

Most development is done on Ubuntu. Other distros may or may not work; see theLinux instructions for some suggestions.

Building the Android client on Windows or Mac is not supported and doesn't work.

Install depot_tools

Clone thedepot_tools repository:

git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

Adddepot_tools to the end of your PATH (you will probably want to put this in your~/.bashrc or~/.zshrc). Assuming you cloneddepot_tools to/path/to/depot_tools:

export PATH="$PATH:/path/to/depot_tools"

Get the code

Create achromium directory for the checkout and change to it (you can call this whatever you like and put it wherever you like, as long as the full path has no spaces):

mkdir~/chromium && cd ~/chromiumfetch--nohooks android

If you don't want the full repo history, you can save a lot of time by adding the--no-history flag tofetch.

Expect the command to take 30 minutes on even a fast connection, and many hours on slower ones.

If you've already installed the build dependencies on the machine (from another checkout, for example), you can omit the--nohooks flag andfetch will automatically executegclient runhooks at the end.

Whenfetch completes, it will have created a hidden.gclient file and a directory calledsrc in the working directory. The remaining instructions assume you have switched to thesrc directory:

cd src

Converting an existing Linux checkout

If you have an existing Linux checkout, you can add Android support by appendingtarget_os = ['linux', 'android'] to your.gclient file (in the directory abovesrc):

echo"target_os = [ 'linux', 'android' ]">>../.gclient

Then rungclient sync to pull the new Android dependencies:

gclient sync

(This is the only difference betweenfetch android andfetch chromium.)

Install additional build dependencies

Once you have checked out the code, run

build/install-build-deps.sh

to get all of the dependencies you need to build on Linux,plus all of the Android-specific dependencies (you need some of the regular Linux dependencies because an Android build includes a bunch of the Linux tools and utilities).

NOTE: For 32-bit builds, the--lib32 command line switch could be used. You may run into issues wheregperf orpkgconf don't get installed, without it. To remedy this, and potentially other missing packages, you will have to install them manually using:

sudo apt-get install{missing_pkg}

Run the hooks

Once you've runinstall-build-deps at least once, you can now run the Chromium-specific hooks, which will download additional binaries and other things you might need:

gclient runhooks

Optional: You can alsoinstall API keys if you want your build to talk to some Google services, but this is not necessary for most development and testing purposes.

Setting up the build

Chromium usesSiso as its main build tool along with a tool calledGN to generate.ninja files. You can create any number ofbuild directories with different configurations. To create a build directory which builds Chrome for Android, rungn args out/Default and edit the file to contain the following arguments:

target_os="android"target_cpu="arm64"# See "Figuring out target_cpu" belowuse_remoteexec=true# Enables distributed builds. See "Faster Builds".is_component_build=false# Unless you do a lot of native code edits. See "Faster Builds".

• You only have to run this once for each new build directory, Siso will update the build files as needed.
• You can replaceDefault with another name, but it should be a subdirectory ofout.
• For other build arguments, including release settings, seeGN build configuration. The default will be a debug component build.
• For more info on GN, rungn help on the command line or read thequick start guide.

Also be aware that some scripts (e.g.tombstones.py,adb_gdb.py) require you to setCHROMIUM_OUTPUT_DIR=out/Default.

Figuring out target_cpu

The value oftarget_cpu determines what instruction set to use for native code. Given a device (or emulator), you can determine the correct instruction set withadb shell getprop ro.product.cpu.abi:

Build Chromium

Build Chromium with Siso or Ninja using the command:

autoninja-Cout/Default chrome_public_apk

(autoninja is a wrapper that automatically provides optimal values for the arguments passed tosiso orninja.)

You can get a list of all of the other build targets from GN by runninggn ls out/Default from the command line. To compile one, pass the GN label to Ninja with no preceding “//” (so, for//chrome/test:unit_tests useautoninja -C out/Default chrome/test:unit_tests).

Multiple Chrome Targets

The Google Play Store allows apps to send customized bundles (.aab files) depending on the version of Android running on a device. Chrome uses this feature to package optimized versions for different OS versions.

1. monochrome_public_bundle (MonochromePublic.aab)
   • minSdkVersion=26 (Oreo). [Deprecated]
   • Contains both Chrome and WebView (to save disk space).
2. trichrome_chrome_bundle (TrichromeChrome.aab)
   • minSdkVersion=29 (Android 10).
   • Native code shared with WebView through a “Static Shared Library APK”:trichrome_library_apk
   • Corresponding WebView target:trichrome_webview_bundle
3. chrome_public_bundle &chrome_public_apk (ChromePublic.aab,ChromePublic.apk)
   • minSdkVersion=29 (Android 10).
   • Used for local development (to avoid building WebView).
   • WebView packaged independently (system_webview_bundle /system_webview_apk).

Updating your checkout

To update an existing checkout, you can run

$ git rebase-update$ gclient sync

The first command updates the primary Chromium source repository and rebases any of your local branches on top of tip-of-tree (aka the Git branchorigin/main). If you don't want to use this script, you can also just usegit pull or other common Git commands to update the repo.

The second command syncs dependencies to the appropriate versions and re-runs hooks as needed.

Installing and Running Chromium on a device

Plug in your Android device

Make sure your Android device is plugged in via USB, and USB Debugging is enabled.

To enable USB Debugging:

• Navigate to Settings > About Phone > Build number
• Click ‘Build number’ 7 times
• Now navigate back to Settings > Developer Options
• Enable ‘USB Debugging’ and follow the prompts

You may also be prompted to allow access to your PC once your device is plugged in.

You can check if the device is connected by running:

third_party/android_sdk/public/platform-tools/adb devices

Which prints a list of connected devices. If not connected, try unplugging and reattaching your device.

Enable apps from unknown sources

Allow Android to run APKs that haven't been signed through the Play Store:

• Enable ‘Unknown sources’ under Settings > Security

In case that setting isn't present, it may be possible to configure it viaadb shell instead:

third_party/android_sdk/public/platform-tools/adb shell settings putglobal verifier_verify_adb_installs0

Build the full browser

autoninja-Cout/Default chrome_public_apk

And deploy it to your Android device:

out/Default/bin/chrome_public_apk install

The app will appear on the device as “Chromium”.

Build Content shell

Wraps the content module (but not the /chrome embedder). Seehttps://www.chromium.org/developers/content-module for details on the content module and content shell.

autoninja-Cout/Default content_shell_apkout/Default/bin/content_shell_apk install

this will build and install an Android apk underout/Default/apks/ContentShell.apk.

Build WebView

Android WebView is a system framework component. Since Android KitKat, it is implemented using Chromium code (based off thecontent module).

If you want to build the complete Android WebView framework component and test the effect of your chromium changes in Android apps using WebView, you should follow theAndroid AOSP + chromium WebView instructions

Running

For Content shell:

out/Default/bin/content_shell_apk launch[--args='--foo --bar'] http://example.com

For Chrome public:

out/Default/bin/chrome_public_apk launch[--args='--foo --bar'] http://example.com

Logging and debugging

Logging is often the easiest way to understand code flow. In C++ you can print log statements using the LOG macro. In Java, refer toandroid_logging.md.

You can see these log viaadb logcat, or:

out/Default/bin/chrome_public_apk logcat

Logcat supports an additional feature of filtering and highlighting user-defined patterns. To use this mechanism, define a shell variable:CHROMIUM_LOGCAT_HIGHLIGHT and assign your desired pattern. The pattern will be used to search for any substring (ie. no need to prefix or suffix it with.*), eg:

export CHROMIUM_LOGCAT_HIGHLIGHT='(WARNING|cr_Child)'out/Default/bin/chrome_public_apk logcat# Highlights messages/tags containing WARNING and cr_Child strings.

Note: bothMessage andTag portion of logcat are matched against the pattern.

To debug C++ code, use one of the following commands:

out/Default/bin/content_shell_apk gdbout/Default/bin/chrome_public_apk gdb

SeeAndroid Debugging Instructions for more on debugging, including how to debug Java code.

Testing

For information on running tests, seeAndroid Test Instructions

Faster Builds

GN Args

Args that affect build speed:

• use_remoteexec = true(default=false)
  • What it does: Enables distributed builds with remote exec API.
• symbol_level = 0(default=1)
  • What it does: Disables most debug information in native code.
    • Stack traces will still show, but be missing frames for inlined functions and source lines.
  • Mostly impacts link time. Lower settings ==> faster links.
  • To disable symbols only in Blink / V8:blink_symbol_level = 0,v8_symbol_level = 0
• is_component_build = false(default=is_debug)
  • See:docs/component_build.md
  • The size of native code for a component build is ~2x that of a non-component build, but link times increase for non-component builds.
  • When mostly iterating on Java code, useis_component_build=false for faster .apk installs.
• is_java_debug = true(default=is_debug)
  • What it does: Disables R8 (whole-program Java optimizer)
• treat_warnings_as_errors = false(default=true)
  • Causes any compiler warnings or lint checks to not fail the build.
  • Allows you to iterate without needing to satisfy static analysis checks.
• android_static_analysis = "build_server"(default="on")
  • Offloads static analysis steps to the build server. Explained below.
  • Set this to"off" if you want to turn off static analysis altogether.
• incremental_install = true(default=false)
  • Makes build and install quite a bit faster. Explained in a later section.
• enable_chrome_android_internal = false(Googlers only)
  • Disables non-public code, which exists even when building public targets.
  • Use this is you do not need to test internal-only things.

Asynchronous Static Analysis

Normally analysis build steps like Lint and Error Prone will run as normal build steps. The build will then wait for all analysis steps to complete successfully. By offloading analysis build steps to a separate build server to be run lazily at a low priority, the actual build can complete much faster.

Note: Since the build completes before the analysis checks finish, the build will not fail if an analysis check fails.

To enable this mode, add the gn args:

android_static_analysis="build_server"

Command output will show up on the terminal that ran the build, as well as inout/Debug/buildserver.log.0.

See the status of the server at any time via:

build/android/fast_local_dev_server.py --print-status-all

Use Remote Execution

Chromium's build can be sped up significantly by using a remote execution system compatible withREAPI. This allows you to benefit from remote caching and executing many build actions in parallel on a shared cluster of workers.

To use Remote Execution, follow the correspondingLinux build instructions.

Incremental Install

Incremental Install uses reflection and sideloading to speed up the edit & deploy cycle (normally < 10 seconds). The initial launch of the apk will be a lot slower on older Android versions (pre-N) where the OS needs to pre-optimize the side-loaded files, but then be only marginally slower after the first launch.

To enable Incremental Install, add the gn args:

incremental_install=true

Some APKs (e.g. WebView) do not work withincremental install = true and are always built as normal APKs. This behavior is controlled vianever_incremental = true.

Installing and Running Chromium on an Emulator

Running on an emulator is the same as on a device. Refer toandroid_emulator.md for setting up emulators.

Tips, tricks, and troubleshooting

Rebuilding libchrome.so for a particular release

These instructions are only necessary for Chrome 51 and earlier.

In the case where you want to modify the native code for an existing release of Chrome for Android (v25+) you can do the following steps. Note that in order to get your changes into the official release, you'll need to send your change for a codereview using the regular process for committing code to chromium.

1. Open Chrome on your Android device and visitchrome://version
2. Copy down the id listed next to “Build ID:”
3. Go tohttp://storage.googleapis.com/chrome-browser-components/BUILD_ID_FROM_STEP_2/index.html
4. Download the listed files and follow the steps in the README.

Building with Docker

To build Chromium for Android using Docker, please follow the instructions in theDocker in Linux build instructions.