---
title: "QLThumbnailCancel(_:)"
framework: quicklook
role: symbol
role_heading: Function
path: "quicklook/qlthumbnailcancel(_:)"
---

# QLThumbnailCancel(_:)

Cancels the computation of the thumbnail.

## Declaration

```swift
func QLThumbnailCancel(_ thumbnail: QLThumbnail!)
```

## Parameters

- `thumbnail`: The thumbnail to cancel.

## Discussion

Discussion If you use QLThumbnailDispatchAsync(_:_:_:) to request the thumbnail, calling this function invokes the completion callback of QLThumbnailDispatchAsync(_:_:_:). If you use synchronous mode, QLThumbnailCopyImage(_:) returns NULL immediately.

## See Also

### Creating thumbnails

- [QLThumbnailImageCreate(_:_:_:_:)](quicklook/qlthumbnailimagecreate(_:_:_:_:).md)
- [QLThumbnailCreate(_:_:_:_:)](quicklook/qlthumbnailcreate(_:_:_:_:).md)
- [QLThumbnailDispatchAsync(_:_:_:)](quicklook/qlthumbnaildispatchasync(_:_:_:).md)
- [QLThumbnailCopyDocumentURL(_:)](quicklook/qlthumbnailcopydocumenturl(_:).md)
- [QLThumbnailCopyImage(_:)](quicklook/qlthumbnailcopyimage(_:).md)
- [QLThumbnailCopyOptions(_:)](quicklook/qlthumbnailcopyoptions(_:).md)
- [QLThumbnailGetContentRect(_:)](quicklook/qlthumbnailgetcontentrect(_:).md)
- [QLThumbnailGetMaximumSize(_:)](quicklook/qlthumbnailgetmaximumsize(_:).md)
- [QLThumbnailGetTypeID()](quicklook/qlthumbnailgettypeid().md)
- [QLThumbnailIsCancelled(_:)](quicklook/qlthumbnailiscancelled(_:).md)