Ok, I just put this code and now I am not getting more errors (I saved the .js as camera.js in the same folder of ViewController.swift) if let userScriptURL = Bundle.main.url(forResource: "camera", withExtension: "js") { let userScriptCode = try! String(contentsOf: userScriptURL) let userScript = WKUserScript(source: userScriptCode, injectionTime: .atDocumentStart, forMainFrameOnly: false) let webConfiguration = WKWebViewConfiguration() webConfiguration.userContentController.addUserScript(userScript) }