# CFStringCreateWithBytes(_:_:_:_:_:) Creates a string from a buffer containing characters in a specified encoding. ``` func CFStringCreateWithBytes(_ alloc: CFAllocator!, _ bytes: UnsafePointer!, _ numBytes: CFIndex, _ encoding: CFStringEncoding, _ isExternalRepresentation: Bool) -> 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. `bytes` A buffer containing characters in the encoding specified by `encoding`. The buffer must *not* contain a length byte (as in Pascal buffers) or any terminating `NULL` character (as in C buffers). `numBytes` The number of bytes in `bytes`. `encoding` The string encoding of the characters in the buffer. `isExternalRepresentation` `true` if the characters in the byte buffer are in an “external representation” format—that is, whether the buffer contains a BOM (byte order marker). This is usually the case for bytes that are read in from a text file or received over the network. Otherwise, pass `false`. ## Return Value An immutable string, 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 This function handles character data in an “external representation” format by interpreting any BOM (byte order marker) character and performing any necessary byte swapping. --- 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)