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# contentType

The content type of the source data for the thumbnail request.

```
var contentType: UTType! { get set }
```

## Discussion

Quick Look Thumbnailing uses the content type of the source data to determine the provider of the thumbnail and the icon styles it applies when you request [`iconMode`](/documentation/QuickLookThumbnailing/QLThumbnailGenerator/Request/iconMode).

If you don’t set this property, Quick Look Thumbnailing derives the content from the file extension. When the file doesn’t have a meaningful extension and you know the content type, set the property directly.

---

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