React Native Animations: Reanimated vs. Animated API

Introduction

Animations are a crucial part of modern mobile app development, enhancing user experience by making interactions feel fluid and intuitive. In React Native, developers have two primary animation libraries to choose from: the built-in Animated API and the more powerful Reanimated library. While both serve the same purpose—creating smooth animations—they differ significantly in performance, flexibility, and complexity.

This post will compare these two solutions, highlighting their strengths, weaknesses, and ideal use cases. We’ll also provide practical examples to help you decide which library best fits your project’s needs.

The Animated API: Built-in but Limited

React Native’s Animated API is the default solution for animations, offering a straightforward way to create basic transitions, interpolations, and gestures. It works by offloading animations to the native thread, avoiding the JavaScript thread bottleneck.

Key Features of the Animated API

1. Declarative Syntax – Define animations using simple JavaScript objects.
2. Basic Animations – Supports common transitions like fadeIn, scale, and translate.
3. Native Driver Support – Improves performance by running animations on the UI thread.

Example: Fade-in Animation with Animated API

Here’s how you can implement a simple fade-in effect:

import React, { useEffect, useRef } from 'react';  
import { Animated, View, StyleSheet } from 'react-native';  

const FadeInView = () => {  
  const fadeAnim = useRef(new Animated.Value(0)).current;  

  useEffect(() => {  
    Animated.timing(fadeAnim, {  
      toValue: 1,  
      duration: 2000,  
      useNativeDriver: true,  
    }).start();  
  }, [fadeAnim]);  

  return (  
    <Animated.View style={{ ...styles.box, opacity: fadeAnim }} />  
  );  
};  

const styles = StyleSheet.create({  
  box: {  
    width: 100,  
    height: 100,  
    backgroundColor: 'blue',  
  },  
});  

export default FadeInView;

Limitations of the Animated API

• Limited Gesture Support – Complex touch interactions require additional libraries like react-native-gesture-handler.
• Performance Issues – Some animations still run on the JavaScript thread, causing jank.
• No Direct Layout Animations – Cannot animate layout changes (e.g., flexbox adjustments) smoothly.

Reanimated: Power and Flexibility

Reanimated is a community-driven library that addresses many of the Animated API’s shortcomings. It introduces a more performant architecture by executing animations entirely on the native thread, even for complex interactions.

Key Advantages of Reanimated

1. Worklets – JavaScript functions that run on the UI thread, eliminating JS thread bottlenecks.
2. Gesture Integration – Seamlessly works with react-native-gesture-handler for advanced touch interactions.
3. Layout Animations – Supports smooth transitions for layout changes (e.g., reordering lists).

Example: Spring Animation with Reanimated

Here’s how to create a spring-based animation with Reanimated 2:

import React from 'react';  
import { StyleSheet, View } from 'react-native';  
import Animated, {  
  useSharedValue,  
  useAnimatedStyle,  
  withSpring,  
} from 'react-native-reanimated';  

const SpringBox = () => {  
  const offset = useSharedValue(0);  

  const animatedStyles = useAnimatedStyle(() => ({  
    transform: [{ translateX: withSpring(offset.value * 100) }],  
  }));  

  return (  
    <View style={styles.container}>  
      <Animated.View style={[styles.box, animatedStyles]} />  
      <Button  
        onPress={() => (offset.value = Math.random())}  
        title="Move"  
      />  
    </View>  
  );  
};  

const styles = StyleSheet.create({  
  container: { flex: 1, justifyContent: 'center', alignItems: 'center' },  
  box: { width: 100, height: 100, backgroundColor: 'red' },  
});  

export default SpringBox;

When to Use Reanimated

• Complex Gestures (e.g., swipe-to-delete, drag-and-drop).
• 60 FPS Animations – For buttery-smooth transitions.
• Shared Element Transitions – Smoothly animate elements between screens.

Performance Comparison

• Animated API is best for simple animations where performance isn’t critical.
• Reanimated is ideal for high-performance apps with complex interactions.

Conclusion

Choosing between Animated API and Reanimated depends on your project’s requirements:

• Use Animated API if you need basic animations with minimal setup.
• Use Reanimated for advanced gestures, layout animations, and smoother performance.

For most modern React Native apps, Reanimated is the superior choice due to its performance optimizations and richer feature set. However, if you’re building a lightweight app with simple transitions, the built-in Animated API might suffice.

By understanding these differences, you can make an informed decision and implement animations that delight users without compromising performance.