®If you are planning a new iPhone app, your developers will soon ask whether to build it with SwiftUI or UIKit. Both are Apple frameworks for building the screens of an iOS app, and both are fully supported. The choice affects how fast your team can work, which iOS versions you can support and how easy the app will be to maintain.
What SwiftUI and UIKit are
UIKit is the older framework. It has been the foundation of iPhone apps since the early days of the platform. Developers build screens by creating views and controllers and telling them step by step how to change when something happens. It is mature, very flexible and extremely well documented. Most large iOS apps that have been around for a while contain a lot of UIKit code.
SwiftUI is Apple's newer framework. Developers describe what each screen should look like for a given state, and the framework works out how to update the display when that state changes. This is called a declarative approach. It usually means less code for the same screen, live previews while designing and a single way of building interfaces across iPhone, iPad, Mac, Apple Watch and Apple TV.
Both use the Swift language, and they can live side by side in the same app. That last point matters more than most comparisons admit.
SwiftUI vs UIKit compared
| Factor | SwiftUI | UIKit |
|---|---|---|
| Style | Declarative, state driven | Imperative, step by step |
| Amount of code | Usually less for standard screens | Usually more |
| Live previews | Built into Xcode | Limited |
| Fine control over layout and behaviour | Good, still improving | Very high |
| Older iOS versions | Newer features need newer iOS | Works on almost any supported version |
| Other Apple platforms | One approach for all of them | Mainly iPhone and iPad |
| Community answers and examples | Growing quickly | Huge, built up over many years |
Where SwiftUI does well
SwiftUI is a strong default for most new apps. Typical business apps are made of lists, forms, detail pages, settings and simple animations, and SwiftUI handles all of these cleanly.
- Faster screen building. Less boilerplate means developers spend more time on the product and less on wiring.
- Easier design iteration. Xcode previews let a developer see changes almost instantly, which shortens the loop with designers.
- Consistent state handling. Because screens are driven by data, it is harder to end up with a screen that shows stale information.
- Future direction. Apple introduces many new features and widgets with SwiftUI in mind, so new projects stay closer to where the platform is going.
The main trade-off is that some newer SwiftUI features only work on recent iOS versions. If your users are mostly on current devices, this is rarely a problem.
Where UIKit still makes sense
UIKit is far from obsolete. It remains the better choice in some situations.
- You must support older iOS versions. Some enterprise or regional audiences keep older devices for a long time.
- You need very precise control. Complex custom text editing, unusual gestures, advanced collection layouts or tight scrolling performance with very large data sets can be easier in UIKit.
- You already have a large UIKit codebase. Rewriting working screens rarely pays off. Adding new screens in SwiftUI while keeping the old ones is usually smarter.
- You depend on libraries built for UIKit. Some mature third-party components still assume UIKit.
Mixing both in one app
You do not have to pick only one. Apple provides bridges in both directions. A SwiftUI screen can host a UIKit view, and a UIKit app can show SwiftUI screens. Many teams build new apps in SwiftUI and drop down to UIKit for the one or two screens that need special handling, such as a camera view or a custom editor.
For existing apps, the common path is gradual. New features are written in SwiftUI, while older screens are migrated only when they need significant changes anyway. This spreads the cost and avoids a risky rewrite.
How to choose
Use this short checklist with your team.
- Check your minimum iOS version. Look at your analytics or your target audience. If most users are on recent versions, SwiftUI is easy to justify.
- List your hardest screens. If two or three screens need very custom behaviour, plan to build those in UIKit inside a SwiftUI app.
- Look at your existing code. New app: start with SwiftUI. Large existing UIKit app: keep it and add SwiftUI gradually.
- Ask about your team's experience. A team strong in one framework will be faster in it. Make sure someone on the team understands both, since most real apps touch both.
- Think about other Apple platforms. If an iPad, Mac or Watch version is on your roadmap, SwiftUI makes sharing work much easier.
For most new apps aimed at current iPhones, the answer is SwiftUI with UIKit used where it is needed. If you are still deciding whether to build natively at all, our guide on Flutter vs React Native covers the cross-platform options.
Frequently asked questions
Is UIKit being replaced by SwiftUI?
Apple continues to support and update UIKit, and SwiftUI itself relies on parts of it behind the scenes. SwiftUI is the direction Apple is pushing for new work, but UIKit will be around for a long time.
Is a SwiftUI app slower than a UIKit app?
For typical business screens, users will not notice a difference. Very demanding screens, such as huge scrolling lists with complex cells, may need careful tuning or a UIKit component. Good engineering matters more than the framework.
Can we move an existing UIKit app to SwiftUI?
Yes, and it can be done gradually. Teams usually build new features in SwiftUI and migrate old screens when they need redesigning, so the app keeps working throughout.
Planning a new iOS app or modernising an existing one? Our mobile app development team works with both SwiftUI and UIKit and can help you pick the right mix.