# CFStringCreateFromExternalRepresentation(_:_:_:) Creates a string from its “external representation.” ``` func CFStringCreateFromExternalRepresentation(_ alloc: CFAllocator!, _ data: CFData!, _ encoding: CFStringEncoding) -> CFString! ``` ## Parameters `alloc` The allocator to use to allocate memory for the new string. Pass `NULL` or [`kCFAllocatorDefault`](/documentation/CoreFoundation/kCFAllocatorDefault) to use the current default allocator. `data` The CFData object containing bytes that hold the characters in the specified encoding. `encoding` The encoding to use when interpreting the bytes in the data argument. ## Return Value An immutable string containing the characters from `data`, or `NULL` if there was a problem creating the object. Ownership follows the [The Create Rule](https://developer.apple.com/library/archive/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029). ## Discussion In the CFData object form, the string can be written to disk as a file or be sent out over a network. If the encoding of the characters in the data object is Unicode, the function reads any BOM (byte order marker) and properly resolves endianness. The [`CFStringCreateExternalRepresentation(_:_:_:_:)`](/documentation/CoreFoundation/CFStringCreateExternalRepresentation(_:_:_:_:)) function complements this function by creating an “external representation” CFData object from a string. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)