Apple provides us the WebKit framework to display web content in windows. Here is a simple example to accomplish a simple web browser depending on the WebKit.

The basic theory is to state an object of WKWebView which will hold all operators, for example back/forward/refresh. In this example, I make a WebViewController to do all things, in which there're some Bar Button Item to do different operators in Navigation Bar and Toolbar, just as the following screenshot shows.



The codes of WebViewController shows as follows.

import UIKit
import WebKit

class WebViewController: UIViewController, WKUIDelegate {

    var webView: WKWebView!
    var urlString: String!
    
    override func loadView() {
        super.loadView()
        let webConfiguration = WKWebViewConfiguration()
        webView = WKWebView(frame: .zero, configuration: webConfiguration)
        webView.uiDelegate = self
        view = webView
    }
    
    deinit {
        webView.removeObserver(self, forKeyPath: #keyPath(WKWebView.estimatedProgress))
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        urlString = "https://wangmingjun.com"
        
        let url = URL(string: urlString)!
        let request = URLRequest(url: url)
        webView.load(request)
        
        webView.addObserver(self, forKeyPath: #keyPath(WKWebView.estimatedProgress), options: .new, context: nil)
    }
    
    @IBAction func doneButtonTapped(_ sender: Any) {
        dismiss(animated: true, completion: nil)
    }
    
    @IBAction func refreshButtonTapped(_ sender: Any) {
        webView.reload()
    }
    
    @IBAction func backButtonTapped(_ sender: Any) {
        webView.goBack()
    }
    
    @IBAction func forwardButtonTapped(_ sender: Any) {
        webView.goForward()
    }
    
    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == "estimatedProgress" {
            if webView.estimatedProgress == 1.0 {
                title = webView.title
            }
        }
    }
    
    @IBAction func actionButtonTapped(_ sender: Any) {
        
        let activityItems = [urlString] as! [String]
        let activityController = UIActivityViewController(activityItems: activityItems, applicationActivities: nil)
        activityController.excludedActivityTypes = [UIActivity.ActivityType.postToFacebook]//, UIActivityType.markupAsPDF]
        present(activityController, animated: true, completion: nil)
    }
    
    @IBAction func safariButtonTapped(_ sender: Any) {
        UIApplication.shared.open(URL(string: urlString)!)
    }
    
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return .lightContent
    }

}

Thanks to Web View Controller – Design+Code.