singular-particular-space/skills/react-native-skills/rules/list-performance-images.md

title, impact, impactDescription, tags

title	impact	impactDescription	tags
Use Compressed Images in Lists	HIGH	faster load times, less memory	lists, images, performance, optimization

Use Compressed Images in Lists

Always load compressed, appropriately-sized images in lists. Full-resolution images consume excessive memory and cause scroll jank. Request thumbnails from your server or use an image CDN with resize parameters.

Incorrect (full-resolution images):

function ProductItem({ product }: { product: Product }) {
  return (
    <View>
      {/* 4000x3000 image loaded for a 100x100 thumbnail */}
      <Image
        source={{ uri: product.imageUrl }}
        style={{ width: 100, height: 100 }}
      />
      <Text>{product.name}</Text>
    </View>
  )
}

Correct (request appropriately-sized image):

function ProductItem({ product }: { product: Product }) {
  // Request a 200x200 image (2x for retina)
  const thumbnailUrl = `${product.imageUrl}?w=200&h=200&fit=cover`

  return (
    <View>
      <Image
        source={{ uri: thumbnailUrl }}
        style={{ width: 100, height: 100 }}
        contentFit='cover'
      />
      <Text>{product.name}</Text>
    </View>
  )
}

Use an optimized image component with built-in caching and placeholder support, such as expo-image or SolitoImage (which uses expo-image under the hood). Request images at 2x the display size for retina screens.