About Regex Tester
Test and debug regular expressions against your own text in real time. See matches highlighted as you type, use capture groups, and toggle flags like global, case-insensitive, and multiline.
How to Use
- Enter your regular expression pattern.
- Set the flags you need (g, i, m, s).
- Paste the text to test against.
- See matches highlighted and inspect capture groups.
Why Use This Tool?
- Accurate — built on precise, well-tested mathematical formulas.
- Instant — all calculations happen client-side for zero latency.
- Private — no data is sent to any server; your information stays on your device.
- Free — no sign-up, no limits, no hidden costs.
Frequently Asked Questions
What do the regex flags g, i, m, and s mean?
g = global (find all matches, not just the first), i = case-insensitive, m = multiline (^ and $ match line starts/ends), and s = dotall (. also matches newlines).
What is a capture group?
Parentheses ( ) create a capture group that extracts part of a match. For example, (\d{4})-(\d{2}) captures a year and month separately so you can reuse them.
Which regex flavour does this use?
It uses the JavaScript (ECMAScript) regex engine built into your browser, so patterns behave exactly as they would in JS code.