WebView Developer Notes

On UWP, there are two variants of WebView:

• WebView - the default WebView implementation, which uses the EdgeHTML rendering engine.
• WebView2 - the new WebView implementation, which uses the Chromium-based Edge rendering engine.

On WinAppSDK, there is only one variant of WebView:

• WebView2 - the new WebView implementation, which uses the Chromium-based Edge rendering engine.

In case of Uno Platform, both WebView and WebView2 are currently provided in both Uno.UI and Uno.WinUI. WebView may be removed in a future release as a breaking change.

Structure of WebView2

WebView2 consists of two components - WebView2 class, which is a Windows App SDK Control and a CoreWebView2, which is a "native" controller, shared among different WebView2 implementations (WPF, WinForms, etc.). The inner CoreWebView2 is accessible from WebView2 via CoreWebView2 property.

Anatomy of WebView and WebView2 in Uno

To make the shared implementation between WebView and WebView2 as large as possible, both controls will have use the CoreWebView2 for most of the logic. The public members of both controls will then act as a proxy to the CoreWebView2. However, the actual platform-specific logic is then in yet another layer - classes that implement the INativeWebView interface. This is the actual place where the platform-bound WebViews reside.

Most of the native logic is provided by the native web view controls - e.g. WKWebView on iOS, WebView on Android.

Navigation event order

Both WebView and WebView2 have the same navigation event order:

• NavigationStarting
• ContentLoading
• DOMContentLoaded

At the end of the navigation, on WebView the either NavigationCompleted or NavigationFailed are raised. WebView2 has only NavigationCompleted.

In WebView, most the events include Uri, but WebView2 uses a unique NavigationId instead. For details on WebView2 event behavior see: https://learn.microsoft.com/microsoft-edge/webview2/concepts/navigation-events