---
title: NSURLErrorFailingURLStringErrorKey
framework: foundation
role: symbol
role_heading: Global Variable
path: foundation/nsurlerrorfailingurlstringerrorkey
---

# NSURLErrorFailingURLStringErrorKey

The URL which caused a load to fail.

## Declaration

```swift
let NSURLErrorFailingURLStringErrorKey: String
```

## Discussion

Discussion The corresponding value is an NSString object. This constant supersedes NSErrorFailingURLStringKey, which was deprecated starting in macOS 10.6.  Both constants refer to the same value for backward-compatibility, but this symbol name has a better prefix.

## See Also

### Keys

- [NSURLErrorFailingURLErrorKey](foundation/nsurlerrorfailingurlerrorkey.md)
- [NSURLErrorFailingURLPeerTrustErrorKey](foundation/nsurlerrorfailingurlpeertrusterrorkey.md)
- [NSURLErrorBackgroundTaskCancelledReasonKey](foundation/nsurlerrorbackgroundtaskcancelledreasonkey.md)
- [URL Session Background Task Cancellation Reasons](foundation/url-session-background-task-cancellation-reasons.md)
- [NSURLErrorNetworkUnavailableReasonKey](foundation/nsurlerrornetworkunavailablereasonkey.md)
- [URLError.NetworkUnavailableReason](foundation/urlerror/networkunavailablereason-swift.enum.md)