WKWebView embed video keeps playing sound after release

You can load blank page [NSURL URLWithString:@"about:blank"]

There is probably better solution though

UPDATE: fixed in iOS 8.3

I'd recommend stopping video with JS code. For example

let stopVideoScript = "var videos = document.getElementsByTagName('video'); for( var i = 0; i < videos.length; i++ ){videos.item(i).pause()}"
self.webView.evaluateJavaScript(stopVideoScript, completionHandler:nil)