WebView Build Instructions

*** promo Building WebView for the first time? Please see the quick start guide first.

[TOC]

Overview

This is meant to be a comprehensive guide for building WebView, within the limits of what is possible in a public chromium checkout. While this is sufficient for most cases, Googlers may wish to consult internal instructions to get a checkout including closed-source code, which is necessary if:

• You work on features depending on this closed-source code
• You want to use the "downstream" targets (ex. system_webview_google_apk), or
• You need to install on a preview Android release

System requirements, tools, etc.

See general Android instructions for:

• System requirements
• Installing depot_tools
• Getting the code or converting a Linux checkout
• Installing build dependencies and running hooks

Device setup

For the minimum requirements, please see Device Setup.

Setting up the build

Configure GN args (run gn args out/Default) as follows:

target_os = "android"

# See "Figuring out target_cpu" below
target_cpu = "arm64"

# Not always necessary, see "Changing package name" below
system_webview_package_name = "..."

# Optional: speeds up build time. For instructions, refer to
# https://chromium.googlesource.com/chromium/src/+/main/docs/linux/build_instructions.md#use-reclient
use_remoteexec = true

Figuring out target_cpu

Please see the Chromium instructions.

Building WebView

Similarly to Chrome, WebView can be compiled with a variety of build targets.

TODO(crbug.com/41454956): document the differences between each target.

First, you should figure out your device's integer API level, which determines which build targets will be compatible with the version of the OS on your device:

adb shell getprop ro.build.version.sdk

*** promo Tip: you can convert the API level integer to the release's dessert codename with this table. This developer guide uses API integers and release letters interchangeably.

Then you can build one of the following targets:

autoninja -C out/Default system_webview_apk

*** promo Note: We focus on system_webview_apk rather than Trichrome because we ship WebView separately from Chrome for stability reasons. This reduces start up time and reduces ANRs. You may see references to Trichrome but this should be considered a historical artefact.

Changing package name

Unlike most Android apps, WebView is part of the Android framework. One of the consequences of this is that the WebView implementation on the device can only be provided by a predetermined set of package names (see details). Depending on the chosen build target, you may need to change the package name to match one of the following:

system_webview_apk uses com.android.webview as the package name by default. If your device allows this package name, continue to the next section. Otherwise, you can change the package name by setting the system_webview_package_name GN arg (ex. system_webview_package_name = "com.google.android.webview").

See internal instructions for the Google-internal build targets (system_webview_google_apk).

*** note Note: TV/car devices have a bug where the release key signed WebView is preinstalled on all Android images, even those signed with dev-keys. Because humans cannot access release keys (use_signing_keys = true provides "developer test keys," not release keys), you must remove the preinstalled WebView (see below).

Removing preinstalled WebView

If WebView is preinstalled (under the chosen package name) in the device's system image, you'll also need to remove the preinstalled APK (otherwise, you'll see signature mismatches when installing). You can skip this step if You chose a package name which is not marked as "(preinstalled)."

Otherwise, you can remove the preinstalled WebView like so:

android_webview/tools/remove_preinstalled_webview.py

*** note If you're using an emulator, make sure to start it with -writable-system before removing the preinstalled WebView.

If the script doesn't work, see the manual steps.

Installing WebView and switching provider

For help connecting your Android device, see the Chromium instructions.

You can install a locally compiled APK like so:

# Install the APK
out/Default/bin/system_webview_apk install

# Tell Android platform to load a WebView implementation from this APK
out/Default/bin/system_webview_apk set-webview-provider

Start running an app

See Start running an app from the quick start.

Troubleshooting

Please see the Troubleshooting section in the quick start.

TODO(ntfschr): document cases here which could arise generally, but wouldn't for the quick start.