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# Quick Look UI

Create previews of files to use inside your macOS app.

## Overview

When showing files in your app, including the ability to quickly preview a file and its content can be helpful to your users. For example, you may want to allow users to zoom into a photo, play back an audio file, and so on. Use the Quick Look framework to show a preview of common file types in your macOS app that allow basic interactions. Quick Look can generate previews for common file types, including:

- iWork and Microsoft Office documents
- Images
- Live Photos
- Text files
- PDFs
- Audio and video files

You can provide previews for your own data types by either rendering a view with your own view controller or by returning a supported preview format such as PDF or HTML.

### Providing Quick Look Previews for your Data Types

To provide Quick Look previews for your own file types, create a Quick Look Preview Extension with either a view controller or data based preview. In either case, add your supported content types to the `QLSupportedContentTypes` array in the `Info.plist` file of the extension.

To provide a view controller based preview extension, set up an <doc://com.apple.documentation/documentation/AppKit/NSViewController> that conforms to [`QLPreviewingController`](/documentation/QuickLookUI/QLPreviewingController). Prepare and display the view within the method [`preparePreviewOfFile(at:completionHandler:)`](/documentation/QuickLookUI/QLPreviewingController/preparePreviewOfFile(at:completionHandler:)).

To provide a data-based preview extension, implement a subclass of [`QLPreviewProvider`](/documentation/QuickLookUI/QLPreviewProvider) to provide a [`QLPreviewReply`](/documentation/QuickLookUI/QLPreviewReply) based on the [`QLFilePreviewRequest`](/documentation/QuickLookUI/QLFilePreviewRequest) that the system provides.

## Topics

### Previews

[`QLPreviewPanel`](/documentation/QuickLookUI/QLPreviewPanel)

A class that implements the Quick Look preview panel to display a preview of a list of items.

[`QLPreviewView`](/documentation/QuickLookUI/QLPreviewView)

A Quick Look preview of an item that you can embed into your view hierarchy.

[`QLPreviewItem`](/documentation/QuickLookUI/QLPreviewItem)

A protocol that defines a set of properties you implement to make a preview of your application’s content.

[`QLPreviewPanelDataSource`](/documentation/QuickLookUI/QLPreviewPanelDataSource)

A protocol that the Quick Look preview panel uses to access the contents of its data source object.

[`QLPreviewPanelDelegate`](/documentation/QuickLookUI/QLPreviewPanelDelegate)

A protocol for the delegate of the Quick Look preview panel.

[`QLPreviewItemLoadingBlock`](/documentation/QuickLookUI/QLPreviewItemLoadingBlock)

A type that defines a block used to load a Quick Look preview item.

### Preview Extensions

[`QLPreviewingController`](/documentation/QuickLookUI/QLPreviewingController)

A protocol for implementing a custom controller to create previews of files.

### Data-based Preview Extensions

[`QLPreviewProvider`](/documentation/QuickLookUI/QLPreviewProvider)

A class that you subclass to provide a data-based Quick Look preview extension.

[`QLFilePreviewRequest`](/documentation/QuickLookUI/QLFilePreviewRequest)

A Quick Look preview request that indicates the content to preview.

[`QLPreviewReply`](/documentation/QuickLookUI/QLPreviewReply)

The class you create when providing a data-based Quick Look preview extension.

[`QLPreviewReplyAttachment`](/documentation/QuickLookUI/QLPreviewReplyAttachment)

An attachment for a Quick Look preview reply that provides additional content for the system to display a preview.


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