# asciiOnlyCharacterClasses(_:) Returns a regular expression that matches only ASCII characters when matching character classes. ``` func asciiOnlyCharacterClasses(_ useASCII: Bool = true) -> Regex.RegexOutput> ``` ## Parameters `useASCII` A Boolean value indicating whether to match only ASCII characters when matching character classes. ## Return Value The modified regular expression. --- 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)