Regex Tester

Yes, completely free with no account or signup required.

JavaScript's built-in RegExp (ECMAScript standard) with flags: global (g), case-insensitive (i), multiline (m), and dotAll (s).

Live match highlighting, capture group extraction, match count, a regex cheat sheet, and one-click patterns for common use cases.

A regular expression (regex) is a sequence of characters that defines a search pattern. It is used to find, match, validate, and transform text in programming languages, editors, and command-line tools.

Enter your pattern in the Pattern field and your test string in the Text field. Matches are highlighted in real time as you type.

Flags modify how the pattern matches. g (global) finds all matches instead of stopping at the first. i (case-insensitive) treats uppercase and lowercase as equal. m (multiline) makes ^ and $ match line starts/ends. s (dotAll) makes . match newlines.

Greedy quantifiers (*, +, {n,m}) match as much as possible. Lazy quantifiers (*?, +?, {n,m}?) match as little as possible. For example, <.+> greedily matches a whole string, while <.+?> lazily matches the shortest possible span.

A capture group is part of the pattern wrapped in parentheses (). The matched text is extracted separately. Named groups use (?<name>...) syntax.

A common email pattern is [a-z0-9._%+-]+@[a-z0-9.-]+.[a-z]{2,}. Click the Email pattern in the cheat sheet to use it instantly.

A lookahead asserts that a pattern must (or must not) follow the current position without consuming characters. (?=...) is a positive lookahead and (?!...) is a negative lookahead.

Use ^ to match the start and $ to match the end. Enable the m flag to make ^ and $ match the start and end of each individual line rather than the whole string.