System WebView Shell

WebView team maintains a “shell”--a thin interface over the WebView APIs--to exercise WebView functionality. The System WebView Shell (AKA “shell browser,” “WebView shell”) is a standalone app implemented in chromium. While often used for manual testing, we also use the shell for automated tests (see our layout and page cycler tests).

This relies on the WebView installed on the system. So if you're trying to verify local changes to WebView, or run against a specific WebView build, you must install WebView first.

Tip: the shell displays the WebView version (the corresponding chromium version number) in the title bar at the top. This can be helpful for checking which WebView version is installed & selected on the device.

Building the shell

$ autoninja -C out/Default system_webview_shell_apk

Installing the shell

# Build and install
$ out/Default/bin/system_webview_shell_apk install

The WebView shell may be preinstalled on a device or emulator. If the signature of the locally built shell does not match the preinstalled shell then the install will fail – usually with this error:

...
path/to/SystemWebViewShell.apk: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE:
Package org.chromium.webview_shell signatures do not match previously installed
version; ignoring!]

If this occurs then delete the preinstalled WebView shell as so:

Note: If using the emulator ensure it is being started with the -writable-system option as per the Writable system partition instructions.

# Remount the /system partition read-write
$ adb root
$ adb remount
# Get the APK path to the WebView shell
$ adb shell pm path org.chromium.webview_shell
package:/system/app/Browser2/Browser2.apk
# Use the APK path above to delete the APK
$ adb shell rm /system/app/Browser2/Browser2.apk
# Restart the Android shell to "forget" about the WebView shell
$ adb shell stop
$ adb shell start

Running the shell

# Launch a URL from the commandline, or open the app from the app launcher
$ out/Default/bin/system_webview_shell_apk launch "https://www.google.com/"

# For more commands:
$ out/Default/bin/system_webview_shell_apk --help

Note: system_webview_shell_apk does not support modifying CLI flags. See https://crbug.com/959425. Instead, you should modify WebView's flags by following commandline-flags.md.