How to force WKWebView to ignore hardware silent switch on iOS?

Question

The ask here is to play all kinds of web sounds regardless of the hardware silent switch , both muted and not muted devices must keep playing the sound in HTML pages while the app is foregrounded. The solution for deprecated UIWebView is quite easy

let localWebView = UIWebView(frame: .zero)
localWebView.allowsInlineMediaPlayback = true
localWebView.mediaPlaybackRequiresUserAction = false

How the same behavior can be achieved for WKWebView?

Answer 1

Update: Added new hack working also for iOS 14(and 15)! (reflected in code, see bottom for extra details).
Since I have a solution to this nontrivial problem, I'd like to share it:

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: #selector(didBecomeActive),
                                               name: NSNotification.Name.UIApplicationDidBecomeActive, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(willResignActive),
                                               name: NSNotification.Name.UIApplicationWillResignActive, object: nil)
    let configuration = WKWebViewConfiguration()
    configuration.allowsInlineMediaPlayback = true
    configuration.mediaTypesRequiringUserActionForPlayback = []
    wkWebView = WKWebView(frame: .zero, configuration: configuration)
}

@objc func willResignActive() {
    disableIgnoreSilentSwitch(wkWebView)
}

@objc func didBecomeActive() {
    //Always creates new js Audio object to ensure the audio session behaves correctly
    forceIgnoreSilentHardwareSwitch(wkWebView, initialSetup: false)
}   

And most importantly in WKNavigationDelegate:

private func disableIgnoreSilentSwitch(_ webView: WKWebView) {
    //Nullifying the js Audio object src is critical to restore the audio sound session to consistent state for app background/foreground cycle
    let jsInject = "document.getElementById('wkwebviewAudio').muted=true;"
    webView.evaluateJavaScript(jsInject, completionHandler: nil)
}

private func forceIgnoreSilentHardwareSwitch(_ webView: WKWebView, initialSetup: Bool) {
    //after some trial and error this seems to be minimal silence sound that still plays
    let silenceMono56kbps100msBase64Mp3 = "data:audio/mp3;base64,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"
    //Plays 100ms silence once the web page has loaded through HTML5 Audio element (through Javascript)
    //which as a side effect will switch WKWebView AudioSession to AVAudioSessionCategoryPlayback

    var jsInject: String
    if initialSetup {
       jsInject =
            "var s=new Audio('\(silenceMono56kbps100msBase64Mp3)');" +
            "s.id='wkwebviewAudio';" +
            "s.play();" +
            "s.loop=true;" +
            "document.body.appendChild(s);"
    } else {
        //Restore sound hack
        jsInject = "document.getElementById('wkwebviewAudio').muted=false;"
    }
    webView.evaluateJavaScript(jsInject, completionHandler: nil)
}

func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
    //As a result the WKWebView ignores the silent switch
    forceIgnoreSilentHardwareSwitch(webView, initialSetup: true)
}

Interestingly a related Safari problem is mentioned here: IOS WebAudio only works on headphones where @Spencer Evans workaround looks very similar to mine.

However when I tried to apply his shorter base64 silence sound it didn't work for WKWebView, so I'm providing my own minimal silence sound tested on iOS12.

Why it works?

Playing an <audio> or <video> element (which in the workaround happens to be non audible silence) changes WKWebView audio session category from AVAudioSessionCategoryAmbient to AVAudioSessionCategoryPlayback. This will be valid until next load request resets it.

It's all great till the app is backgrounded. But upon subsequent foregrounding things will break in 2 possible ways:

• user needs to tap for the sounds to reappear
• rarely no user input will help and the WKWebView lands in semi frozen state

To counter that^ the hack is reverted with disableIgnoreSilentSwitch(wkWebView) and later reenabled with forceIgnoreSilentHardwareSwitch(wkWebView, initialSetup: false)

Since WKWebView core runs in an external process it cannot be accessed the way UIWebView shared (with our app) AVAudioSession can be.

Verified for:
iOS 11.4
iOS 12.4.1
iOS 13.3
iOS 14.1
iOS 14.5.1
iOS 14.8
iOS 15.0

iOS 14 update
Situation got pretty bad in iOS 14 where obsolete audio tag .src=null trick stopped working. Technically .src=null does work for a very short window of time (one can revert the hack using .src during initial setup). However once the silence loop is playing it becomes useless.

The new trick relies on .mute which miraculously works across all iOS versions including iOS14 (but only when accessing documentById directly not a var). No mediacenter when locking the screen neither. It took a lot of research, but we got it.