Why SwiftUI feels janky: it ditches Core Animation, the backbone of iOS smoothness

dotey · x · 2026-09-16

Developer kzzzf explains why SwiftUI apps can feel janky: SwiftUI isn't "native" in the classic sense — it drops Core Animation, the key element that kept iOS animations smooth since the original iPhone.

In SwiftUI, animations run in-app without CA backing. Block the main thread and a SwiftUI ball stalls, while UIKit's keeps moving because its animations run on the render server.

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