Android

On Android the WebView is a Play-updatable component, independent of the OS, so the fix for a below-floor engine is usually two taps. The guard's job is to say which component, and to open its listing.

What is checked

The provider is WebViewCompat.getCurrentWebViewPackage(context) from androidx.webkit — the public WebView API on 26+, reflection into WebViewFactory below. The same call returned the provider on API 24, 33, 34 and 36.

The package is never a constant. On Android 7–9 it is typically Android System WebView (com.google.android.webview); on 10+ many devices use Chrome's Trichrome library; some OEMs ship their own. Whatever WebViewCompat reports is what the dialog names and what the Update button deep-links to.

The Chromium major is read from the start of the provider's versionName (109 from 109.0.5414.123) and compared, inclusively, with min_chromium — 111 by default.

Below the floor

• The WebView is neutralized: JavaScript off first, so even a page that does commit cannot run a line of the app's bundle; then hidden (INVISIBLE), so not even a blank page paints under the dialog; then any navigation in flight is stopped and replaced with about:blank — the one URL the Rust navigation hook still allows.
• An AlertDialog names the provider by its own label ("Android System WebView", "Chrome", an OEM name), with Open Play Store and Close app.
• Open Play Store fires market://details?id=<provider>; if nothing handles it, https://play.google.com/store/apps/details?id=<provider>. Fired and caught, not resolved in advance, so no <queries> entry is needed. The dialog stays up — a user who comes back without updating finds the same dialog, not a blank app.
• Close app calls finishAndRemoveTask().
• The dialog is not cancellable by Back or by tapping outside.
• If the device reported no provider package at all, the dialog has no Update button — there is nothing to link to.

The plugin's manifest is empty on purpose: no permissions and no <queries>. getCurrentWebViewPackage needs neither — the provider's PackageInfo is handed to the app by the WebView factory, not looked up through PackageManager, so Android 11's package-visibility filtering does not apply.

An unreadable version boots

An unreadable version (no provider, an OEM versionName that does not start with a Chromium major) is Verdict::Unknown: the app boots, with a warning in the log. An unreadable version is not evidence of an old engine, and an "update your WebView" dialog in front of a current device is the same dead end as the white screen.

Release builds and R8

The plugin's classes are kept by proguard-rules.pro. Tauri's PluginManager reaches the plugin class and its commands by reflection, so R8 cannot see any reference to them; a stripped plugin would mean "No command engine found", only in release, only on a minified app — and the guard silently never running.

Not measured

Every device run so far used a debug APK. The keep rule is in place, but R8 has not been run against it — see what verification does not prove.

Android 7.x does not reach the guard

Android 7.x (API 24/25) does not reach the guard on stock Tauri. Tauri 2.11.6 crashes in TauriActivity.onCreate on API 24/25 — jackson-databind 2.15.3's static initialiser needs java.lang.BootstrapMethodError (API 26) — before any plugin is constructed. Measured on the API 24 emulator; tauri-apps/tauri#8788, open.

Either:

• raise minSdk to 26, or
• force an older Jackson in your generated Gradle project, as examples/tauri-app/android-7-jackson-workaround.zsh does (reported working in that issue, and how the Chromium 53 arm here was verified). The generated Gradle project is gitignored, so it has to be patched after every tauri android init.

The plugin does not do this to your app: overriding a Tauri dependency is your call. Upstream dependencies tracks when the workaround can go.

Kotlin tests

android/ is a Gradle subproject with no wrapper of its own, so its JVM tests run from the example's generated Android project:

cd examples/tauri-app && npm install && npx tauri android init
npx tauri android build --debug --target aarch64 --apk
cd src-tauri/gen/android && ./gradlew :tauri-plugin-webview-guard:testDebugUnitTest