# data(using:allowLossyConversion:) Returns an `NSData` object containing a representation of the receiver encoded using a given encoding. ``` func data(using encoding: UInt, allowLossyConversion lossy: Bool) -> Data? ``` ## Parameters `encoding` A string encoding. For possible values, see [`NSStringEncoding`](/documentation/Foundation/NSStringEncoding). `lossy` If , then allows characters to be removed or altered in conversion. ## Return Value An `NSData` object containing a representation of the receiver encoded using `encoding`. Returns `nil` if `flag` is and the receiver can’t be converted without losing some information (such as accents or case). ## Discussion If `flag` is and the receiver can’t be converted without losing some information, some characters may be removed or altered in conversion. For example, in converting a character from `NSUnicodeStringEncoding` to `NSASCIIStringEncoding`, the character ‘Á’ becomes ‘A’, losing the accent. This method creates an external representation (with a byte order marker, if necessary, to indicate endianness) to ensure that the resulting `NSData` object can be written out to a file safely. The result of this method, when lossless conversion is made, is the default “plain text” format for encoding and is the recommended way to save or transmit a string object. --- 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)