---
title: NSSystemExtensionUsageDescriptionKey
framework: systemextensions
role: symbol
role_heading: Global Variable
path: systemextensions/nssystemextensionusagedescriptionkey
---

# NSSystemExtensionUsageDescriptionKey

A message that tells the user why the app is trying to install a system extension bundle.

## Declaration

```swift
let NSSystemExtensionUsageDescriptionKey: String
```

## Discussion

Discussion This key is required for all system extensions except DriverKit extensions, and must be in the extension’s Info.plist file. Failure to include this key results in an error at activation time. For DriverKit extensions, use OSBundleUsageDescriptionKey instead.

## See Also

### Usage descriptions

- [OSBundleUsageDescriptionKey](systemextensions/osbundleusagedescriptionkey.md)