# WKScriptMessageHandlerWithReply An interface for responding to messages from JavaScript code running in a webpage. ``` @MainActor protocol WKScriptMessageHandlerWithReply : NSObjectProtocol ``` ## Overview Adopt the [`WKScriptMessageHandlerWithReply`](/documentation/WebKit/WKScriptMessageHandlerWithReply) protocol when your app needs to receive JavaScript messages from a web view and provide an appropriate response. When JavaScript code sends a message that specifically targets your message handler, WebKit calls your handler’s [`userContentController(_:didReceive:replyHandler:)`](/documentation/WebKit/WKScriptMessageHandlerWithReply/userContentController(_:didReceive:replyHandler:)) method. Use that method to process the message and provide your response. To call your message handler from JavaScript, send a message to `window.webkit.messageHandlers..postMessage()` in your code. You specify the name of your message handler when you add it to a [`WKUserContentController`](/documentation/WebKit/WKUserContentController) object. > Note: > If you don’t need to provide a response back to JavaScript, implement your message handler using the ``doc://com.apple.webkit/documentation/WebKit/WKScriptMessageHandler`` protocol instead. ## Topics ### Receiving Messages [`userContentController(_:didReceive:replyHandler:)`](/documentation/WebKit/WKScriptMessageHandlerWithReply/userContentController(_:didReceive:replyHandler:)) Tells the handler that a webpage sent a script message that included a reply. [`WKScriptMessage`](/documentation/WebKit/WKScriptMessage) An object that encapsulates a message sent by JavaScript code from a webpage. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)