Regex Tester – Test Regular Expressions with Live Highlighting

A regular expression (regex) is a sequence of characters that defines a search pattern. It is used to find, match, and replace text. For example, the pattern \d{3}-\d{4} matches phone number formats like 555-1234. Regex is supported in JavaScript, Python, Java, and almost every programming language.

g (global): find all matches, not just the first. i (case-insensitive): match uppercase and lowercase equally. m (multiline): makes ^ and $ match the start/end of each line, not just the string. s (dotAll): makes the . character match newlines as well as regular characters.

Named capture groups let you label parts of a match using the syntax (?<name>...). For example, (?<year>\d{4})-(?<month>\d{2}) would capture the year and month from a date string as named properties. Named groups make your regex more readable and allow accessing match parts by name rather than by index.

Special characters in regex (. * + ? ^ $ { } [ ] | ( ) \) must be escaped with a backslash if you want to match them literally. For example, to match a period, use \. (not just .) because . in regex means "any character". To match a dollar sign, use \$.