# encodeBytes(_:length:forKey:) Encodes a given number of bytes from a given C array of bytes and associates them with a key. ``` func encodeBytes(_ bytes: UnsafePointer?, length: Int, forKey key: String) ``` ## Parameters `bytes` A C array of bytes to encode. `length` The number of bytes from `bytesp` to encode. `key` The key with which to associate the encoded value. This value must not be `nil`. ## See Also [`decodeBytes(forKey:returnedLength:)`](/documentation/Foundation/NSKeyedUnarchiver/decodeBytes(forKey:returnedLength:)) Decodes a stream of bytes associated with a given key. --- 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)