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# PreviewRegistry

A protocol that the system uses to locate previews at runtime.

```
protocol PreviewRegistry
```

## Overview

Preview macros make use of this protocol on your behalf.
Don’t use it directly. Instead, use one of the preview macros, like
<doc://com.apple.documentation/documentation/SwiftUI/Preview(_:body:)>.

> Important: If you define a preview registry directly, the behavior is
> undefined.

## Topics

### Making a preview

[`static func makePreview() throws -> Preview`](/documentation/DeveloperToolsSupport/PreviewRegistry/makePreview())

[`static var preview: Preview`](/documentation/DeveloperToolsSupport/PreviewRegistry/preview)

[`static var column: Int`](/documentation/DeveloperToolsSupport/PreviewRegistry/column)

[`static var fileID: String`](/documentation/DeveloperToolsSupport/PreviewRegistry/fileID)

[`static var line: Int`](/documentation/DeveloperToolsSupport/PreviewRegistry/line)

### Getting errors

[`struct PreviewUnavailable`](/documentation/DeveloperToolsSupport/PreviewUnavailable)

An error that the system throws when a preview is unavailable at runtime.


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