UIStackView in place that's another UIKit component under your belt – good job! The addition of multitasking and size classes helps make the app much more polished, and I think you have the seeds of a great app here.
If you want to try extending this project, the sensible place to start is in the URL entry: if users don't type "http://" before their web site addresses the app fails, which isn't very helpful.
Another smart place to improve the app is inside the
setDefaultTitle() method: it just writes Multibrowser in the navigation bar while leaving a large white space in the center – hardly intuitive, and it wouldn't be hard to add a placeholder label in there telling users what to do.
One of the most effective motivators of success is sharing your progress with other people – when you tell folks what you're doing and what you've learned, it encourages you to come back for more, which in turn will help you reach your app development goals faster.
So, now that you've done all the hard work it's time to share your success: tell folks that you've completed this project, either by clicking the button below to start composing a tweet, or by writing your own message from scratch. This will definitely encourage you to keep learning, but it will also help other folks discover my work – thank you!
Paul Hudson is the creator of Hacking with Swift, the most comprehensive series of Swift books in the world. He's also the editor of Swift Developer News, the maintainer of the Swift Knowledge Base, and a speaker at Swift events around the world. If you're curious you can learn more here.