---
title: Animate Transform and Opacity Instead of Layout Properties
impact: HIGH
impactDescription: GPU-accelerated animations, no layout recalculation
tags: animation, performance, reanimated, transform, opacity
---

## Animate Transform and Opacity Instead of Layout Properties

Avoid animating `width`, `height`, `top`, `left`, `margin`, or `padding`. These trigger layout recalculation on every frame. Instead, use `transform` (scale, translate) and `opacity` which run on the GPU without triggering layout.

**Incorrect (animates height, triggers layout every frame):**

```tsx
import Animated, {
  useAnimatedStyle,
  withTiming,
} from 'react-native-reanimated';

function CollapsiblePanel({
  expanded,
  children,
}: React.PropsWithChildren<{ expanded: boolean }>) {
  const animatedStyle = useAnimatedStyle(() => ({
    height: withTiming(expanded ? 200 : 0), // triggers layout on every frame
    overflow: 'hidden',
  }));

  return <Animated.View style={animatedStyle}>{children}</Animated.View>;
}
```

**Correct (animates scaleY, GPU-accelerated):**

```tsx
import Animated, {
  useAnimatedStyle,
  withTiming,
} from 'react-native-reanimated';

function CollapsiblePanel({
  expanded,
  children,
}: React.PropsWithChildren<{ expanded: boolean }>) {
  const animatedStyle = useAnimatedStyle(() => ({
    transform: [{ scaleY: withTiming(expanded ? 1 : 0) }],
    opacity: withTiming(expanded ? 1 : 0),
  }));

  return (
    <Animated.View
      style={[{ height: 200, transformOrigin: 'top' }, animatedStyle]}
    >
      {children}
    </Animated.View>
  );
}
```

**Correct (animates translateY for slide animations):**

```tsx
import Animated, {
  useAnimatedStyle,
  withTiming,
} from 'react-native-reanimated';

function SlideIn({
  visible,
  children,
}: React.PropsWithChildren<{ visible: boolean }>) {
  const animatedStyle = useAnimatedStyle(() => ({
    transform: [{ translateY: withTiming(visible ? 0 : 100) }],
    opacity: withTiming(visible ? 1 : 0),
  }));

  return <Animated.View style={animatedStyle}>{children}</Animated.View>;
}
```

GPU-accelerated properties: `transform` (translate, scale, rotate), `opacity`. Everything else triggers layout.
