WebView (WebView2)

Uno Platform supports two WebView controls - a legacy WebView and a modernized WebView2 control. For new development, we strongly recommend WebView2 as it will get further improvements in the future.

WebView2 is currently supported on Windows, Android, iOS, macOS (Catalyst), Desktop (Windows), and WebAssembly.

Basic usage

You can include the WebView2 control anywhere in XAML:

<WebView2 x:Name="MyWebView" Source="https://platform.uno/" />

To manipulate the control from C#, first ensure that you call its EnsureCoreWebView2Async method:

await MyWebView.EnsureCoreWebView2Async();

Afterward, you can perform actions such as navigating to an HTML string:

MyWebView.NavigateToString("<html><body><p>Hello world!</p></body></html>");
Important

For Skia WPF, you should add <PackageReference Include="Microsoft.Web.WebView2" Aliases="WpfWebView" /> to your csproj.

WebAssembly support

In case of WebAssembly, the control is supported via a native <iframe> element. This means all <iframe> browser security considerations and limitations also apply to WebView:

Executing JavaScript

When a page is loaded inside the WebView2 control, you can execute custom JavaScript code. To do this, call the ExecuteScriptAsync method:

webView.NavigateToString("<div id='test' style='width: 10px; height: 10px; background-color: blue;'></div>");
// Renders a blue <div>

await webView.ExecuteScriptAsync("document.getElementById('test').style.backgroundColor = 'red';");
// The <div> is now red.

The method can also return a string result, with returned values being JSON-encoded:

await webView.ExecuteScriptAsync("1 + 1"); // Returns a string containing 2
await webView.ExecuteScriptAsync($"(1 + 1).toString()"); // Returns a string containing "2"
await webView.ExecuteScriptAsync("eval({'test': 1})"); // Returns a string containing {"test":1}

JavaScript to C# communication

WebView2 enables sending web messages from JavaScript to C# on all supported targets. In your web page, include code that sends a message to the WebView2 control if available. Since Uno Platform runs on multiple targets, you need to use the correct approach for each. We recommend creating a reusable function like the following:

function postWebViewMessage(message){
    try{
        if (window.hasOwnProperty("chrome") && typeof chrome.webview !== undefined) {
            // Windows
            chrome.webview.postMessage(message);
        } else if (window.hasOwnProperty("unoWebView")) {
            // Android
            unoWebView.postMessage(JSON.stringify(message));
        } else if (window.hasOwnProperty("webkit") && typeof webkit.messageHandlers !== undefined) {
            // iOS and macOS (Catalyst)
            webkit.messageHandlers.unoWebView.postMessage(JSON.stringify(message));
        }
    }
    catch (ex){
        alert("Error occurred: " + ex);
    }
}

// Usage:
postWebViewMessage("hello world");
postWebViewMessage({"some": ['values',"in","json",1]});

Note: Make sure not to omit the JSON.stringify calls for Android, iOS, and macOS as seen in the snippet above, as they are crucial to transfer data correctly.

To receive the message in C#, subscribe to the WebMessageReceived event:

webView.WebMessageReceived += (s, e) =>
{
    Debug.WriteLine(e.WebMessageAsJson);
};

The WebMessageAsJson property contains a JSON-encoded string of the data passed to postWebViewMessage above.

Navigating to web content in the application package

To load local web content bundled with the application, you can use the SetVirtualHostNameToFolderMapping method. This allows you to set a virtual hostname that maps to a folder within the package, from which the web content will be loaded:

await webView.EnsureCoreWebView2Async();
webView.CoreWebView2.SetVirtualHostNameToFolderMapping(
    "UnoNativeAssets",
    "WebContent",
    CoreWebView2HostResourceAccessKind.Allow);
webView.CoreWebView2.Navigate("http://UnoNativeAssets/index.html");

This will navigate to the index.html file stored in the WebContent folder. This folder must be included in a platform-specific location on each platform:

  • On Windows, it should be directly in the root of the YourApp.Windows project and all its contents should be set to Content build action
  • On iOS, it should be inside the Resources folder and all its contents should be set to BundleResource build action
  • On Android, it should be inside the Assets folder and all its contents should be set to AndroidAsset build action

To avoid duplication, you can put the files in a non-project-specific location and add them via linking, e.g.:

<BundleResource Include="..\LinkedFiles\WebContent\css\site.css" Link="iOS\Resources\WebContent\css\site.css" />

The web files can reference each other in a relative path fashion, for example, the following HTML file:

<html>
<head>
    <script src="js/site.js" type="text/javascript"></script>
</head>
<body>
    ...
</body>
</html>

Is referencing a site.js file inside the js subfolder.

iOS and macOS (Catalyst) specifics

From MacOS, inspecting applications using WebView2 controls using the Safari Developer Tools is possible. Here's a detailed guide on how to do it. To make this work, enable this feature in your app by adding the following capabilities in your App.Xaml.cs:

public App()
{
    this.InitializeComponent();
#if __IOS__
    Uno.UI.FeatureConfiguration.WebView2.IsInspectable = true;
#endif
}
Important

This feature will only work for security reasons when the application runs in Debug mode.