How to control the sites a WKWebView can visit using WKNavigationDelegate

Swift version: 5.4

Paul Hudson @twostraws September 19th 2019

By default a WKWebView can navigate to any links the user selects, but it’s common to want to restrict that. It only takes three steps to accomplish this:

Make your view controller conform to WKNavigationDelegate.
Assign your view controller to be your web view’s navigationDelegate.
Implement the decidePolicyFor method to decide whether each URL should be allowed or denied.

Let’s try it out now. First, make your view controller conform to WKNavigationDelegate.

Second, set your view controller to be the navigationDelegate property of your web view. This might be done in viewDidLoad(), but you can also change the delegate dynamically. Either way, you need to use this code:

yourWebView.navigationDelegate = self

Finally, implement the decidePolicyFor method. This is the only part that takes any work: you need to pull out the host of the URL that was requested, run any checks you want to make sure it’s OK, then call the decisionHandler() closure with either .allow to allow the URL or .cancel to deny access.

Here’s an example to get you started:

func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: @escaping (WKNavigationActionPolicy) -> Void) {
    if let host = navigationAction.request.url?.host {
        if host.contains("hackingwithswift.com") {
            decisionHandler(.allow)
            return
        }
    }

    decisionHandler(.cancel)
}

That code will allow navigation only to URLs that contain “hackingwithswift.com”.