# folding(options:locale:) Creates a string suitable for comparison by removing the specified character distinctions from a string. ``` func folding(options: NSString.CompareOptions = [], locale: Locale?) -> String ``` ## Parameters `options` Any combination of the [`caseInsensitive`](/documentation/Foundation/NSString/CompareOptions/caseInsensitive), [`widthInsensitive`](/documentation/Foundation/NSString/CompareOptions/widthInsensitive), and [`diacriticInsensitive`](/documentation/Foundation/NSString/CompareOptions/diacriticInsensitive) comparison options. `locale` The locale to use for the folding operation. Pass `nil` to use the system locale. ## Return Value A string created by performing a character folding operation with the specified options and locale. ## Discussion When working with text—especially text in Latin script—it’s often useful to compare strings in such a way that ignores differences in case (uppercase or lowercase), width (full-width or half-width), and/or diacritics (accents and other marks). To accomplish this, you may use one of the methods described in Identifying and Comparing Strings, passing one or more options specified by the [`NSString.CompareOptions`](/documentation/Foundation/NSString/CompareOptions) type as appropriate. If you’re performing many such comparisons, you may instead, as an optimization, perform a single folding operation on the string and store the result, passing that into a more efficient comparison method. For example, if you were determining the case-insensitive (that is, “HELLO”, “hello”, and “Hello” are all considered equal) intersection of two sets of strings, instead of calling the [`localizedCaseInsensitiveCompare(_:)`](/documentation/Foundation/NSString/localizedCaseInsensitiveCompare(_:)) method for each pair of strings, you might first normalize both sets of strings by calling the [`folding(options:locale:)`](/documentation/Foundation/NSString/folding(options:locale:)) method, passing the [`caseInsensitive`](/documentation/Foundation/NSString/CompareOptions/caseInsensitive) option and the current locale, and then compare each pair of folded strings using the [`isEqual(to:)`](/documentation/Foundation/NSString/isEqual(to:)) method. > Tip: > Character folding operations using the ``doc://com.apple.foundation/documentation/Foundation/NSString/folding(options:locale:)`` method are often more performant than the equivalent string transform using the ``doc://com.apple.foundation/documentation/Foundation/NSString/applyingTransform(_:reverse:)`` method. Rules for how characters are folded may vary, depending on the locale. For example, when folding a string containing the character “I” (`U+0049` `LATIN CAPITAL LETTER I`) and specifying the [`caseInsensitive`](/documentation/Foundation/NSString/CompareOptions/caseInsensitive) comparison option, an English-speaking locale returns “i” (`U+0069` `LATIN SMALL LETTER I`), and a Turkish-speaking locale returns “ı” (`U+0131 LATIN SMALL DOTLESS I`). > Note: > The result of character folding operations may not be suitable for display to users, and should be used only for internal processing. --- 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)