Regular Expression Tester & Matcher

g (global): find all matches instead of stopping at the first. i (case-insensitive): treat uppercase and lowercase as equal. m (multiline): makes ^ and $ match start/end of each line, not just the whole string. s (dotAll): makes the dot match newlines too. u (Unicode): enables full Unicode support including named character class escapes.

Parentheses create a capturing group. Everything matched inside the parentheses is captured separately. For example, a pattern like (year)-(month)-(day) on a date string captures three groups. Named groups use the (?<name>...) syntax. The tool shows all captured groups per match in different colors.

Greedy quantifiers (*, +, ?) match as much text as possible. Lazy versions (*?, +?, ??) match as little as possible. For example, matching an HTML tag greedily on a string with multiple tags will match from the first opening tag all the way to the last closing tag. Adding ? after the quantifier makes it stop at the first closing tag instead.

The tool uses JavaScript (ECMAScript) regex, which supports: character classes like [a-z], anchors ^ and $, lookaheads and lookbehinds, named capture groups, Unicode property escapes, and backreferences. PCRE-only features like atomic groups and possessive quantifiers are not supported.

Escape them with a backslash. A backslash before a dot matches a literal dot, not any character. A backslash before an asterisk matches a literal asterisk. To match a literal backslash, use two backslashes. Inside character classes [], most special characters lose their special meaning and match literally.