---
title: uid
framework: Core Audio
role: symbol
role_heading: Instance Property
platforms: [macOS 15.0+]
path: coreaudio/audiohardwarebox/uid
---

# uid

A String that contains a persistent identifier for the box object. A box’s UID is persistent across boots. The content of the UID string is a black box and may contain information that is unique to a particular instance of an box’s hardware or unique to the CPU. Therefore they are not suitable for passing between CPUs or for identifying similar models of hardware.

## Declaration

```swift
var uid: String { get throws }
```