AppLocale
This tool on every surface: CLI · MCP · Python · JavaScript · Go · Java · .NET
Read or set the language one app runs in. These call app_locale.
AppLocale
public IList<string> AppLocale(string app)
public IList<string> AppLocale(string app, string tags)
Language tags pinned for an app; empty means it follows the device.
Runs one app in a chosen language; an empty tag follows the device again. Android 13 and later. What this confirms is that the device stored the tag, not that the app has a translation for it, so check the screen. Relaunch the app for it to re-render.
Examples
Run one app in Japanese
device.AppLocale("org.wikipedia", "ja-JP");
The same call from the command line, mobium locale org.wikipedia ja-JP, printed on an Android 15 emulator:
org.wikipedia set to ja-JP — the device stored it; whether org.wikipedia has that translation is not something Android reports, so check the screen
On a device

mobium launch org.wikipedia on an Android 15 emulator