What is the mock webview?

3D WebView's native Android, iOS, visionOS, WebGL, and UWP plugins can't run in the Editor, so a mock webview implementation is used by default while running in the Editor:

mock webview

However, you can actually load and render web content in the editor by also importing 3D WebView for Windows and macOS into the project:

actual webview

This is highly recommended because iterating in the Editor can save you significant development time. The different 3D WebView packages are designed to work together seamlessly, so all you need to do is import the packages into the same project, and 3D WebView automatically detects and uses the correct plugin at runtime and build time. The only thing to keep in mind is that the packages must be of the same minor version. For example, v4.7 of 3D WebView for Android requires v4.7 of 3D WebView for Windows and macOS.