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# NSURLErrorFailingURLStringErrorKey

The URL which caused a load to fail.

```
let NSURLErrorFailingURLStringErrorKey: String
```

## Discussion

The corresponding value is an [`NSString`](/documentation/Foundation/NSString) object.

This constant supersedes [`NSErrorFailingURLStringKey`](/documentation/Foundation/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.

---

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