Configuration

Everything is configured on tauri_plugin_webview_guard::Builder, in Rust, at registration. There is no runtime configuration, no tauri.conf.json section, and no switch: a registered guard is a live guard.

Every option has a default, so Builder::new().build() — or its shorthand tauri_plugin_webview_guard::init() — is a complete, working guard at Tailwind v4's floor with English copy.

Builder options

Option	Default	Meaning
.min_chromium(u32)	111	Minimum Chromium major, Android. Inclusive: 111 lets 111 through and blocks 110. Compared against the major of the provider's versionName.
.min_ios(impl Into<String>)	"16.4"	Minimum iOS version, major.minor or major.minor.patch. Inclusive. Parsed strictly when .build() runs — "16.4-beta" is refused.
.android_copy(AndroidCopy)	English, below	The Android dialog's title, message and two button labels.
.ios_copy(IosCopy)	English, below	The iOS alert's title and message.
.build()	—	The plugin. Panics if min_ios does not parse — a constant in your source, wrong on every launch, so it fails the first tauri dev. Builder::floor() validates without building.

The defaults are exported as constants, DEFAULT_MIN_CHROMIUM (111) and DEFAULT_MIN_IOS (OsVersion 16.4.0), for an app that wants to derive its floor from them.

How versions are compared

• Android: the Chromium major is the leading run of digits of the provider's versionName, up to the first dot — 109 from 109.0.5414.123 (chromium_major). Anything else, including no provider at all, is Verdict::Unknown.
• iOS: OsVersion is one to three dot-separated non-negative integers, nothing else. Missing components read as zero, so "16.4" is 16.4.0 and compares equal to the 16.4.0 that ProcessInfo.operatingSystemVersion reports. The minor is compared, not only the major.
• Unknown boots. 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. The app boots, with a warning in the log.

Validating in a test

Builder::floor() returns the validated Floor (or a ParseVersionError) without building a plugin, so an app's own test can check its configuration without a Tauri runtime:

let floor = tauri_plugin_webview_guard::Builder::new()
    .min_chromium(120)
    .min_ios("17.2")
    .floor()
    .unwrap();
assert_eq!(floor.min_chromium, 120);

The dialog copy

The one rule every string follows: name the component that is out of date, and never tell the user to update the app. The app is current; "update this app" sends them to a listing with nothing to install.

Three placeholders are substituted in Rust, once, before the text reaches the native side — so Kotlin and Swift show exactly the text the unit tests assert on:

Placeholder	Android	iOS
{component}	The provider's own label, as PackageManager reports it — "Android System WebView", "Chrome", an OEM name	iOS
{installed}	The provider's versionName, e.g. 109.0.5414.123	e.g. 16.3.1
{required}	The configured Chromium major, e.g. 111	e.g. 16.4

If the provider reports no label, or a blank one, {component} falls back to "Android System WebView", which is what the stock provider calls itself.

Defaults

Android  title    Update {component}
         message  This app needs {component} version {required} or newer to display
                  correctly. This phone has version {installed}.

                  The app itself is up to date. Update {component} from the Play Store,
                  then open the app again.
         buttons  Open Play Store · Close app

iOS      title    Update iOS to continue
         message  This app needs iOS {required} or later. This iPhone runs iOS {installed}.

                  The app itself is up to date. Update iOS in Settings › General ›
                  Software Update, then open the app again.

The Android title and two buttons are deliberately unlike Android 14's own "This app was built for an older version of Android" warning, which uses the app name as title and a single OK.

The iOS alert has no buttons: iOS has no public URL that opens Software Update (openSettingsURLString opens this app's own settings page — a dead end dressed as a way forward), and apps are not meant to quit themselves.

AndroidCopy and IosCopy

Struct	Fields
AndroidCopy	title, message, update_button, close_button
IosCopy	title, message

All fields are String, and all four Android strings are required: an empty button label would render as an untappable blank. Both implement Default with the English text above.

Translating it

A French app, for example:

use tauri_plugin_webview_guard::{AndroidCopy, Builder};

Builder::new().android_copy(AndroidCopy {
    title: "Mettez à jour {component}".into(),
    message: "Cette application a besoin de {component} {required} ou plus récent. \
              Ce téléphone a la version {installed}.\n\n\
              L'application elle-même est à jour : mettez à jour {component} \
              depuis le Play Store, puis rouvrez-la."
        .into(),
    update_button: "Ouvrir le Play Store".into(),
    close_button: "Fermer".into(),
})