---
title: extension
framework: coreservices
role: symbol
role_heading: Instance Property
path: coreservices/lsiteminforecord/1442123-extension
---

# extension

A Core Foundation string object specifying theitem’s filename extension; see the CFString Reference inthe Core Foundation Reference Documentation for a description ofthe CFStringRef datatype.

## Declaration

```swift
var `extension`: Unmanaged<CFString>!
```