WebView Build Instructions

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:

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 fresh builds (Googlers-only)
use_goma = true

# Optional: 64-bit APKs include 32-bit & 64-bit code for broader compatibility.
# You can disable building the 32-bit "secondary ABI" to speed up compiles, but
# this crashes apps with their own 32-bit code.
build_apk_secondary_abi = false

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(https://crbug.com/956315): 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

Then you can build one of the following targets:

# For L-M (21-23) devices (also works for N+, see "Important Notes for N-P")
autoninja -C out/Default system_webview_apk

# For N-P (24-28) devices (not including TV/car devices)
autoninja -C out/Default monochrome_public_apk

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. Depending on the chosen build target, you may need to change the package name to match one of the following:

API level	Has GMS vs. AOSP?	Allowed package names
L-M	AOSP	`com.android.webview`
L-M	Has GMS	`com.google.android.webview`
N-P	AOSP	`com.android.webview`
N-P (TV/car devices)	Has GMS	`com.google.android.webview`
N-P (other devices)	Has GMS	`com.android.chrome` `com.chrome.beta` `com.chrome.dev` `com.chrome.canary` `com.google.android.apps.chrome` `com.google.android.webview` (see Important notes for N-P)

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

monochrome_public_apk‘s package name defaults to org.chromium.chrome, so you need to modify the package name or choose system_webview_apk instead. We don’t have a GN arg for this, but you can ask the team for help modifying build files for local development.

See internal instructions for the Google-internal variants of the build targets (system_webview_google_apk, monochrome_apk).

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 either of the following is true:

You have an N+ device (and chose a package name other than com.android.chrome, com.android.webview, com.google.android.webview), or
You're a Googler using signing keys per internal instructions

Otherwise, you can remove the preinstalled WebView like so:

android_webview/tools/remove_preinstalled_webview.py

Important notes for N-P

If you have an Android build from N-P (and, it uses the Google WebView configuration), then the com.google.android.webview package will be disabled by default. More significantly, installing a locally compiled APK won't work, since the on-device WebViewUpdateService will immediately uninstall such updates. To unblock local development, you can re-enable the WebView package and disable this behavior from WebViewUpdateService with:

# Only necessary if you're using the 'com.google.android.webview' package name
adb shell cmd webviewupdate enable-redundant-packages

Installing WebView and switching provider

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

You can install a locally compiled APK like so (substitute system_webview_apk with the chosen build target name):

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

# Only on N+: 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.