# CFHTTPMessageAppendBytes(_:_:_:) Appends data to a `CFHTTPMessage` object. ``` func CFHTTPMessageAppendBytes(_ message: CFHTTPMessage, _ newBytes: UnsafePointer, _ numBytes: CFIndex) -> Bool ``` ## Parameters `message` The message to modify. `newBytes` A reference to the data to append. `numBytes` The length of the data pointed to by `newBytes`. ## Return Value `TRUE` if the data was successfully appended, otherwise `FALSE`. ## Discussion This function appends the data specified by `newBytes` to the specified message object which was created by calling [`CFHTTPMessageCreateEmpty(_:_:)`](/documentation/CFNetwork/CFHTTPMessageCreateEmpty(_:_:)). The data is an incoming serialized HTTP request or response received from a client or a server. While appending the data, this function deserializes it, removes any HTTP-based formatting that the message may contain, and stores the message in the message object. You can then call [`CFHTTPMessageCopyVersion(_:)`](/documentation/CFNetwork/CFHTTPMessageCopyVersion(_:)), [`CFHTTPMessageCopyBody(_:)`](/documentation/CFNetwork/CFHTTPMessageCopyBody(_:)), [`CFHTTPMessageCopyHeaderFieldValue(_:_:)`](/documentation/CFNetwork/CFHTTPMessageCopyHeaderFieldValue(_:_:)), and [`CFHTTPMessageCopyAllHeaderFields(_:)`](/documentation/CFNetwork/CFHTTPMessageCopyAllHeaderFields(_:)) to get the message’s HTTP version, the message’s body, a specific header field, and all of the message’s headers, respectively. If the message is a request, you can also call [`CFHTTPMessageCopyRequestURL(_:)`](/documentation/CFNetwork/CFHTTPMessageCopyRequestURL(_:)) and [`CFHTTPMessageCopyRequestMethod(_:)`](/documentation/CFNetwork/CFHTTPMessageCopyRequestMethod(_:)) to get the message’s request URL and request method, respectively. If the message is a response, you can also call [`CFHTTPMessageGetResponseStatusCode(_:)`](/documentation/CFNetwork/CFHTTPMessageGetResponseStatusCode(_:)) and [`CFHTTPMessageCopyResponseStatusLine(_:)`](/documentation/CFNetwork/CFHTTPMessageCopyResponseStatusLine(_:)) to get the message’s status code and status line, respectively. --- 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)