A Regex Tester (regular expression tester) lets you write a pattern and immediately see which parts of a test string it matches. It speeds up development by giving instant visual feedback without running code.
This tool uses the native JavaScript RegExp engine built into your browser. It supports the full ES2018+ regex syntax including named capture groups, lookbehind assertions, Unicode property escapes, and the dotAll (s) flag.
Wrap parts of your pattern in parentheses, e.g. (\w+)@(\w+). Each parenthesised sub-pattern is a capture group. The tool displays every group's value separately under each match in the Match Results panel.
g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line boundaries), s (dotAll — . matches newlines), u (full Unicode), and y (sticky). You can combine them freely in the Flags field.
An error appears when the browser's regex parser cannot compile your pattern — for example unmatched brackets, invalid escape sequences, or unsupported syntax. The error message from the parser is shown to help you fix it quickly.
No. All matching and highlighting runs entirely inside your browser using JavaScript. Nothing is transmitted over the network, so your test data stays completely private.
The Explanation panel breaks your pattern into individual tokens and shows a plain-English label under each one (e.g. "digit", "word boundary", "literal"). A summary sentence at the bottom describes what the overall pattern matches.
Yes. Paste multi-line text into the Test String field. Add the m flag to make ^ and $ match individual line boundaries, and the s flag if you need . to cross newlines.
Without the g (global) flag the engine stops after the first match. Add g to your flags to highlight every occurrence in the test string.
Yes, completely free — no account, no sign-up, no usage limits, forever.
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