About the Regex Tester
Regular expressions (regex) are patterns used to match, search, and manipulate text. They power form validation, search-and-replace, log parsing, and countless other tasks — but they're notoriously hard to get right without testing against real input.
This regex tester lets you write a JavaScript-flavored pattern, toggle flags, and see live, highlighted matches against your test string, along with any capture groups. It runs in your browser for instant feedback.
Features
- Live, highlighted matching as you type
- Toggle flags: global, ignore-case, multiline, dotall, unicode
- See capture groups for each match
- Safe against runaway patterns, fully client-side
How to use
- Enter your regular expression in the pattern field.
- Toggle the flags you need (g, i, m, s, u).
- Type or paste your test string to see matches highlighted.
Frequently asked questions
Which regex flavor does this use?
It uses the JavaScript (ECMAScript) regular expression engine, the same one in browsers and Node.js. Syntax may differ slightly from PCRE, Python, or Java regex.
What do the flags mean?
g matches all occurrences, i ignores case, m makes ^ and $ match line boundaries, s lets . match newlines, and u enables full Unicode matching.