---
title: PreviewContextKey
framework: swiftui
role: symbol
role_heading: Protocol
path: swiftui/previewcontextkey
---

# PreviewContextKey

A key type for a preview context.

## Declaration

```swift
protocol PreviewContextKey
```

## Overview

Overview The default value is nil.

## Topics

### Setting a default

- [defaultValue](swiftui/previewcontextkey/defaultvalue.md)
- [Value](swiftui/previewcontextkey/value.md)

## See Also

### Setting a context

- [previewContext(_:)](swiftui/view/previewcontext(_:).md)
- [PreviewContext](swiftui/previewcontext.md)