---
title: preferredFilenameExtension
framework: uniformtypeidentifiers
role: symbol
role_heading: Instance Property
path: uniformtypeidentifiers/uttype-swift.struct/preferredfilenameextension
---

# preferredFilenameExtension

The preferred filename extension for the type.

## Declaration

```swift
var preferredFilenameExtension: String? { get }
```

## Discussion

Discussion If available, the preferred (first available) tag of class filenameExtension. Many types require the generation of a filename; for example, when saving a file to disk. If not nil, the value of this property is the best available filename extension for this type. The value of this property is equivalent to, but more efficient than: type.tags[.filenameExtension]?.first

## See Also

### Obtaining tags

- [preferredMIMEType](uniformtypeidentifiers/uttype-swift.struct/preferredmimetype.md)
- [tags](uniformtypeidentifiers/uttype-swift.struct/tags.md)