# addingPercentEscapes(using:) Returns a representation of the receiver using a given encoding to determine the percent escapes necessary to convert the receiver into a legal URL string. ``` func addingPercentEscapes(using enc: UInt) -> String? ``` ## Parameters `enc` The encoding to use for the returned string. If you are uncertain of the correct encoding you should use [`NSUTF8StringEncoding`](/documentation/Foundation/NSUTF8StringEncoding). ## Return Value A representation of the receiver using `encoding` to determine the percent escapes necessary to convert the receiver into a legal URL string. Returns `nil` if `encoding` cannot encode a particular character. ## Discussion It may be difficult to use this function to “clean up” unescaped or partially escaped URL strings where sequences are unpredictable. See for more information. ## See Also [`- stringByAddingPercentEncodingWithAllowedCharacters:`](/documentation/Foundation/NSString/addingPercentEncoding(withAllowedCharacters:)) Returns a new string made from the receiver by replacing all characters not in the specified set with percent-encoded characters. [`stringByRemovingPercentEncoding`](/documentation/Foundation/NSString/removingPercentEncoding) Returns a new string made from the receiver by replacing all percent encoded sequences with the matching UTF-8 characters. --- 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)