---
title: NSUnderlyingErrorKey
framework: foundation
role: symbol
role_heading: Global Variable
path: foundation/nsunderlyingerrorkey
---

# NSUnderlyingErrorKey

The corresponding value is an error that was encountered in an underlying implementation and caused the error that the receiver represents to occur.

## Declaration

```swift
let NSUnderlyingErrorKey: String
```

## See Also

### Constants

- [NSURLErrorKey](foundation/nsurlerrorkey.md)
- [NSFilePathErrorKey](foundation/nsfilepatherrorkey.md)
- [NSHelpAnchorErrorKey](foundation/nshelpanchorerrorkey.md)
- [NSLocalizedDescriptionKey](foundation/nslocalizeddescriptionkey.md)
- [NSLocalizedFailureErrorKey](foundation/nslocalizedfailureerrorkey.md)
- [NSLocalizedFailureReasonErrorKey](foundation/nslocalizedfailurereasonerrorkey.md)
- [NSLocalizedRecoveryOptionsErrorKey](foundation/nslocalizedrecoveryoptionserrorkey.md)
- [NSLocalizedRecoverySuggestionErrorKey](foundation/nslocalizedrecoverysuggestionerrorkey.md)
- [NSRecoveryAttempterErrorKey](foundation/nsrecoveryattemptererrorkey.md)
- [NSStringEncodingErrorKey](foundation/nsstringencodingerrorkey.md)
- [NSDebugDescriptionErrorKey](foundation/nsdebugdescriptionerrorkey.md)
- [NSMultipleUnderlyingErrorsKey](foundation/nsmultipleunderlyingerrorskey.md)