Platform Differences

This library wraps platform-native file viewers, so behavior differs between iOS, Android, and web.

Comparison

Behavior	iOS	Android	Web
Preview style	In-app modal (QuickLook)	External app (Intent chooser)	New browser tab (window.open)
Promise resolution	Resolves when user dismisses	Resolves immediately after launch	Resolves immediately, even if the tab was blocked
Multi-file preview	Swipeable gallery	Not supported	One tab per file
Editing/markup	Built-in markup tools	Not supported	Not supported
Thumbnails	QLThumbnailGenerator	Not supported	Not supported (throws)
Events	onWillDismiss, onDismiss, onEditedFile, onSavedEditedCopy	None	None
Remote files	Download to temp + preview	Download to cache + launch	Browser fetches the URL directly
Request headers	Supported	Supported	Ignored
Chooser title	Not applicable	Customizable via chooserTitle	Not applicable
canPreview	QLPreviewController.canPreview	Checks installed handlers	Always true

iOS Details

On iOS, QLPreviewController is presented as a modal view controller. The user stays in your app and can dismiss the preview to return. This means:

• You know when the preview is dismissed (onDismiss event)
• You can react to edits (onEditedFile, onSavedEditedCopy)
• The promise resolves after dismissal, so you can chain actions:

await ExpoQuickLook.previewFile({ uri: path });
// User has dismissed the preview
console.log('Preview closed');

Android Details

On Android, an Intent is fired and the system picks an app to handle it. This means:

• Your app goes to the background
• You don't know when the user is done viewing
• The promise resolves right after launch
• No events are available

await ExpoQuickLook.previewFile({ uri: path });
// Intent was launched — user may still be viewing
console.log('Intent launched');

Custom Chooser Title

On Android, customize the "Open with" dialog title:

await ExpoQuickLook.previewFile({
  uri: path,
  chooserTitle: 'View document with',
});

Web Details

On web there is no native preview controller, so the file is handed off to the browser by opening it in a new tab. This means:

• Your app keeps running; the file opens in a separate tab
• You don't know when the user is done viewing — no events fire
• The promise resolves immediately, without knowing whether the browser actually opened the tab (a blocked pop-up can't be detected)
• requestOptions.headers are ignored (the browser fetches the URL itself)
• Only http(s): and blob: URIs work. Browsers refuse to open data: URLs in a new tab, and file:// paths aren't reachable from a web page
• canPreview always returns true, and generateThumbnail throws an ERR_UNAVAILABLE error

await ExpoQuickLook.previewFile({ uri: 'https://example.com/doc.pdf' });
// A new browser tab was opened

note

Browsers block pop-ups that aren't triggered by a direct user gesture. Call previewFile / previewFiles from an event handler (e.g. an onPress), not from an effect or timeout, or the tab may be blocked. previewFiles opens one tab per URI, so multiple tabs are especially likely to be blocked.

Writing Cross-Platform Code

Use Platform.OS to handle differences:

import { Platform } from 'react-native';

await ExpoQuickLook.previewFile({ uri: path });

if (Platform.OS === 'ios') {
  // Preview was dismissed — safe to clean up
} else {
  // Intent launched — file may still be in use
}

Use canPreview to check if a file type is supported before attempting to open it:

const supported = await ExpoQuickLook.canPreview(path);
if (!supported) {
  // Show fallback UI
}