---
title: "provideThumbnail(for:_:)"
framework: quicklookthumbnailing
role: symbol
role_heading: Instance Method
path: "quicklookthumbnailing/qlthumbnailprovider/providethumbnail(for:_:)"
---

# provideThumbnail(for:_:)

Creates a thumbnail of a custom file type for a specific request.

## Declaration

```swift
func provideThumbnail(for request: QLFileThumbnailRequest, _ handler: @escaping (QLThumbnailReply?, (any Error)?) -> Void)
```

## Parameters

- `request`: The request that contains information about the thumbnail that you need to provide, such as the URL to the file.
- `handler`: The completion handler to call when you finish creating a thumbnail. Call the completion handler with a doc://com.apple.quicklookthumbnailing/documentation/QuickLookThumbnailing/QLThumbnailReply if you can provide a thumbnail or with an doc://com.apple.documentation/documentation/Foundation/NSError if you can’t create a thumbnail. The platform doesn’t draw a thumbnail if you pass an error to the handler or the reply is nil. You can call the handler asynchronously after the method has returned.

## Mentioned in

Providing Thumbnails of Your Custom File Types

## Discussion

Discussion To provide a thumbnail for a custom file type, subclass QLThumbnailProvider, implement this method, and return a QLThumbnailReply that either contains a drawing block or the URL to an image file.