---
title: identifier
framework: foundation
role: symbol
role_heading: Instance Property
path: foundation/nsusernotification/identifier
---

# identifier

A string that uniquely identifies a notification.

## Declaration

```swift
var identifier: String? { get set }
```

## Discussion

Discussion The identifier is unique to a notification. A notification delivered with the same identifier as an existing notification replaces the existing notification rather than causing the display of a new notification.

## See Also

### Display Information

- [title](foundation/nsusernotification/title.md)
- [subtitle](foundation/nsusernotification/subtitle.md)
- [informativeText](foundation/nsusernotification/informativetext.md)
- [contentImage](foundation/nsusernotification/contentimage.md)
- [response](foundation/nsusernotification/response.md)
- [responsePlaceholder](foundation/nsusernotification/responseplaceholder.md)