Capture redirect url in wkwebview in ios

(This answers the slightly more general question of how to detect a URL redirection in WKWebView, which is the search that lead me to this page.)

Short answer

Use WKNavigationDelegate's webView(_:didReceiveServerRedirectForProvisionalNavigation:) function and examine WKWebView's URL property.

Longer answer

There are a couple of places you could detect a server-side redirect.

On iOS 10.3.3 and iOS 11.0, the sequence of events I observe when loading a URL that gets redirected by the server is:

1. The WKNavigationDelegate function webView(_:decidePolicyFor:decisionHandler:) is called for the original URL request. WKWebView's URL property is set to the original URL.

2. The WKNavigationDelegate function webView(_:didStartProvisionalNavigation:) is called for the original URL request. WKWebView's URL property is set to the original URL.

3. The WKWebView's URL property is updated by WebKit to the redirection URL. (You'll only know about this if you are key-value observing the property.)

4. The WKNavigationDelegate function webView(_:decidePolicyFor:decisionHandler:) is called for the redirected URL request. WKWebView's URL property is then redirection URL.

5. The WKNavigationDelegate function webView(_:didReceiveServerRedirectForProvisionalNavigation:) is called. WKWebView's URL property is the redirection URL.

(Note: On the iOS 11.0 simulator I have seen steps 3 and 4 reversed, with the URL property unchanged in webView(_:decidePolicyFor:decisionHandler:), which actually seems like a sensible ordering, but I haven't observed this on a device.)

It seems like the webView(_:didReceiveServerRedirectForProvisionalNavigation:) is built explicitly for the purpose of detecting redirects so is probably the preferred option, although the redirect could be possibly be inferred at steps 3 or 4 but only if you can be sure that there are no other causes of navigational change.

After trying all the solutions, finally this one works for me using Swift 5 and WKWebView.This solution implements KVO for Swift

var webView: WKWebView?
var webViewObserver: NSKeyValueObservation?

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    webView = WKWebView(frame: self.view.bounds)
    webViewObserver = webView?.observe(\.url, options: .new, changeHandler: {
        (currentWebView, _) in
        //      Here you go the new path
        currentWebView.url
    })
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    webViewObserver?.invalidate()
}

Swift 5 Boom

Very easy way

func webView(_ webView: WKWebView, didReceiveServerRedirectForProvisionalNavigation navigation: WKNavigation!) {
    if let url = webView.url?.absoluteString{
        print("url = \(url)")
    }
}

For me, using decidePolicyFor navigation delegate's method didn't work.

It didn't work because WKNavigationDelegate's method

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void)

will only be called when there is a full-page reload. To be able to catch all WKWebView's request URL changes, a Key-Value observer will have to be placed on the WKWebView's URL property.

First, in viewDidLoad add:

webView.addObserver(self, forKeyPath: "URL", options: .new, context: nil)

Second, add observeValue method

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == #keyPath(WKWebView.url) {
            // Whenever URL changes, it can be accessed via WKWebView instance
            let url = webView.url
        }
    }

Credits to Sven: https://forums.developer.apple.com/thread/117073

If you are facing a situation that your WebView doesn't open a PDF file or simply the url resolves to nothing, because the WebView's redirect URL doesn't come through you can use WKUIDelegate function webView(_:createWebViewWith:for:windowFeatures:) to capture the failed call and load the request again like:

extension WebViewWrapper: WKUIDelegate {

 func webView(_ webView: WKWebView, createWebViewWith configuration: WKWebViewConfiguration, for navigationAction: WKNavigationAction, windowFeatures: WKWindowFeatures) -> WKWebView? {
     if navigationAction.targetFrame == nil || navigationAction.targetFrame?.isMainFrame == false {
         webView.load(navigationAction.request)
     }
     return nil
 }

}

Use this WKNavigationDelegate method. I got redirect url from sourceFrame.request

public func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Swift.Void) {
        let urlString = navigationAction.sourceFrame.request.url?.absoluteString ?? ""
        print("\(urlString)")
        decisionHandler(.allow)
 }