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# isExcludedFromBackupKey

A key for indicating whether the system excludes the resource from all backups of app data.

```
static let isExcludedFromBackupKey: URLResourceKey
```

## Discussion

The value of this key is a read-write Boolean [`NSNumber`](/documentation/Foundation/NSNumber) object.

Use this property to exclude cache and other app support files that aren’t necessary in a backup. Set this property each time you save a file because some common file operations cause this property to reset to `false`.

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