---
title: key
framework: avfoundation
role: symbol
role_heading: Instance Property
path: avfoundation/avmutablemetadataitem/key
---

# key

The key for a mutable metadata item.

## Declaration

```swift
@NSCopying var key: (any NSCopying & NSObjectProtocol)? { get set }
```

## See Also

### Accessing keys and key spaces

- [keySpace](avfoundation/avmutablemetadataitem/keyspace.md)