regular expression

Also known as regex, regexp, regxp, RegExp, rational expression, Complement operator (regular expressions), regular expressions, rational expressions

sequence of characters that forms a search pattern

AI overview

A regular expression is a sequence of characters that you can use to search for and find specific text patterns in documents or data. It matters because it lets you quickly locate, extract, or replace information without having to manually search through everything yourself.

AI-generated from the Wikipedia summary — may contain errors.

Described at

RegExr: Learn, Build, & Test RegEx

Regular expression tester with syntax highlighting, PHP / PCRE & JS Support, contextual help, cheat sheet, reference, and searchable community patterns.

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Edit the Expression & Text to see matches. Roll over matches or the expression for details. PCRE & JavaScript flavors of RegEx are supported. Validate your expression with Tests mode. The side bar includes a Cheatsheet, full Reference, and Help. You can also Save & Share with the Community and view patterns you create or favorite in My Patterns. Explore results with the Tools below. Replace & List output custom results. Details lists capture groups. Explain describes your expression in plain English. Build a suite of tests that your expression should (or should not) match. Create new tests with the 'Add Test' button. Click a test to edit the name, type, & text. Any unsaved changes will be lost. Saved patterns & favorites will be migrated to your account.

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Wikidata facts

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Stack Exchange tag: stackoverflow.com/tags/regex
Commons category: Regex

~40 min read

Article

Blue highlights show the match results of the regular expression pattern: /r[aeiou]+/g (lowercase r followed by one or more lowercase vowels).

A regular expression (shortened as regex or regexp), sometimes referred to as a rational expression, is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation. Regular expression techniques are developed in theoretical computer science and formal language theory.