Thumbnails

iOS Only

generateThumbnail uses QLThumbnailGenerator, which is only available on iOS.

Generate thumbnails for local files:

const thumbnail = await ExpoQuickLook.generateThumbnail({
  uri: '/path/to/file.pdf',
  size: { width: 200, height: 200 },
});

// thumbnail.uri    — file:// URI to the generated PNG
// thumbnail.width  — actual pixel width
// thumbnail.height — actual pixel height

Options

Option	Type	Default	Description
uri	string	required	Local file path (remote URLs not supported)
size	{ width, height }	required	Requested thumbnail size in points
scale	number	device scale	Pixel scale multiplier

Scale Parameter

The scale parameter controls the pixel density of the output:

// Default: uses device scale (2x on most iPhones, 3x on Pro models)
const thumb = await ExpoQuickLook.generateThumbnail({
  uri: path,
  size: { width: 200, height: 200 },
});
// On a 3x device: output is 600x600 pixels

// Explicit scale
const thumb3x = await ExpoQuickLook.generateThumbnail({
  uri: path,
  size: { width: 200, height: 200 },
  scale: 3,
});
// Always 600x600 pixels regardless of device

Output Size

The actual output dimensions may differ from the requested size — the system preserves the file's aspect ratio. A 200x200 request for a landscape PDF may return a 200x150 thumbnail.

Local Files Only

generateThumbnail only works with local files. Passing a remote URL will throw an error:

// This will throw
await ExpoQuickLook.generateThumbnail({
  uri: 'https://example.com/file.pdf',
  size: { width: 200, height: 200 },
});

// Download first, then generate
// Use expo-file-system or fetch to download, then pass the local path

Supported File Types

Any file type that QuickLook supports can generate a thumbnail: PDFs, images, Office documents, text files, and more.