Lifecycle and performance

WebView ownership

There are three useful ownership patterns:

Pattern	Use case	Native WebView lifetime
Normal InAppWebView	One screen owns the WebView	Ends when the widget/controller is disposed
InAppWebViewKeepAlive	Temporary widget detach or route replacement	Retained across reattachment
InAppWebViewPreloader	Known destination that should open faster	Starts headless, then transfers to inline

The owner must be created outside build(). A Flutter rebuild must not be treated as a request to create a new native WebView.

Safe lifecycle sequence

create -> prepare -> attach -> ready -> detach/retain -> reattach -> dispose

Dispose is idempotent. Once disposal begins, new events and asynchronous operations should not be sent to the native WebView. Pending callbacks keep their existing result contract and complete once.

Avoiding cold starts

• Keep InAppWebViewKeepAlive stable while a screen is temporarily removed.
• Use InAppWebViewPreloader when the destination and initial settings are known before navigation.
• Keep the initial settings stable; changing profile, container, incognito, or data-store settings usually requires a new native WebView.
• Do not clear cache or cookies as a generic performance workaround.
• Do not reload a page merely because the Flutter widget rebuilt.

Event pressure

Scroll, progress, JavaScript bridge, and WebMessage callbacks can be high frequency. Application callbacks should avoid expensive synchronous work, large map copies, and unnecessary state updates. Coalesce UI updates when the application only needs the latest value.

Memory trade-off

Retaining a WebView preserves page state but also retains its renderer, JavaScript context, callbacks, and data-store references. Keep only the WebViews that the user is likely to revisit. Always dispose retained instances when the owning feature or session ends.

Performance checklist

• Measure release/profile builds, not only debug builds.
• Record the Android WebView provider or iOS version with measurements.
• Measure first usable frame separately from onLoadStop.
• Test repeated attach/detach and dispose/recreate cycles.
• Check memory after navigation to a heavy page and after disposal.
• Treat provider, renderer, and OS behavior as separate from Flutter widget rebuild performance.