---
title: unknown
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/urlerror/unknown
---

# unknown

The URL Loading System encountered an error that it can’t interpret.

## Declaration

```swift
static var unknown: URLError.Code { get }
```

## Discussion

Discussion This can occur when an error originates from a lower level framework or library. Whenever this error code is received, it is a bug, and should be reported to Apple.

## See Also

### Error codes

- [appTransportSecurityRequiresSecureConnection](foundation/urlerror/apptransportsecurityrequiressecureconnection.md)
- [backgroundSessionInUseByAnotherProcess](foundation/urlerror/backgroundsessioninusebyanotherprocess.md)
- [backgroundSessionRequiresSharedContainer](foundation/urlerror/backgroundsessionrequiressharedcontainer.md)
- [backgroundSessionWasDisconnected](foundation/urlerror/backgroundsessionwasdisconnected.md)
- [badServerResponse](foundation/urlerror/badserverresponse.md)
- [badURL](foundation/urlerror/badurl.md)
- [callIsActive](foundation/urlerror/callisactive.md)
- [cancelled](foundation/urlerror/cancelled.md)
- [cannotCloseFile](foundation/urlerror/cannotclosefile.md)
- [cannotConnectToHost](foundation/urlerror/cannotconnecttohost.md)
- [cannotCreateFile](foundation/urlerror/cannotcreatefile.md)
- [cannotDecodeContentData](foundation/urlerror/cannotdecodecontentdata.md)
- [cannotDecodeRawData](foundation/urlerror/cannotdecoderawdata.md)
- [cannotFindHost](foundation/urlerror/cannotfindhost.md)
- [cannotLoadFromNetwork](foundation/urlerror/cannotloadfromnetwork.md)