# Regex A regular expression. ``` struct Regex

``` ## Overview Regular expressions are a concise way of describing a pattern, which can help you match or extract portions of a string. You can create a `Regex` instance using regular expression syntax, either in a regex literal or a string. ``` // 'keyAndValue' is created using a regex literal let keyAndValue = /(.+?): (.+)/ // 'simpleDigits' is created from a pattern in a string let simpleDigits = try Regex("[0-9]+") ``` You can use a `Regex` to search for a pattern in a string or substring. Call `contains(_:)` to check for the presence of a pattern, or `firstMatch(of:)` or `matches(of:)` to find matches. ``` let setting = "color: 161 103 230" if setting.contains(simpleDigits) { print("'\(setting)' contains some digits.") } // Prints "'color: 161 103 230' contains some digits." ``` When you find a match, the resulting [`Regex.Match`](/documentation/Swift/Regex/Match) type includes an [`output`](/documentation/Swift/Regex/Match/output) property that contains the matched substring along with any captures: ``` if let match = setting.firstMatch(of: keyAndValue) { print("Key: \(match.1)") print("Value: \(match.2)") } // Key: color // Value: 161 103 230 ``` When you import the `RegexBuilder` module, you can also create `Regex` instances using a clear and flexible declarative syntax. Using this style, you can combine, capture, and transform regexes, `RegexBuilder` types, and custom parsers. > Note: > Prior to Swift 6, > you might need to write `#/myregex/#` instead of `/myregex/` > when you make a regular expression using a literal. > For more information, > see [Regular Expression Literals](https://docs.swift.org/swift-book/documentation/the-swift-programming-language/lexicalstructure/#Regular-Expression-Literals) in *[The Swift Programming Language](https://docs.swift.org/swift-book/)*. --- 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)