Swift Save a Webpage in WKWebView

I want to be able to save any website in a WKWebView, and restore it at anytime through another button.

I tried downloading the HTML of the website:

public func getHtml(completion: @escaping (String?, URL?) -> Void) {
        webView.evaluateJavaScript("document.documentElement.outerHTML.toString()") { html, error in
            let html = html as? String
            completion(html, self.webView.url)
        }
}

and restoring the html using: webView.loadHTMLString(html, baseURL: url)

But loading the html results in losing the formatting for the UI: https://i.stack.imgur.com/Y3S7W.png

Is there a way to save / restore the formatting of the url?