Reanimated

In a project, the install is checked at three points: react-native-reanimated and react-native-worklets in the dependencies at compatible versions (the compatibility table is in the docs), the react-native-worklets/plugin Babel plugin last in babel.config.js, and a native rebuild after installing. The “Native part of Reanimated doesn’t seem to be initialized” error almost always comes from a Metro cache or a skipped native build.

The API to know: useSharedValue, useAnimatedStyle, withTiming, withSpring, withDecay, the withDelay, withRepeat, withSequence modifiers, and useAnimatedScrollHandler for anything driven by scroll. The most common pitfall is reading a shared value’s .value during React render: you get the JS-thread value, not the one of the animation in flight. The second is doing heavy work inside a worklet, which then blocks the UI thread instead of the JS thread.

Reanimated 4 requires the New Architecture; a project still on the old one has to stay on 3.x. CSS animations (animationName, transitionProperty on an Animated.View) cover the simple cases with less code and are a good entry point for a team coming from the web. To measure, the Performance panel in React Native DevTools shows whether an animation is falling back onto the JS thread.