Regex Tester
Write a regular expression and watch every match highlight live in your test text, with flags and capture groups visible.
How to use the Regex Tester
- Enter your regular expression and any flags.
- Paste the text you want to test against.
- Review the highlighted matches and captured groups.
About the Regex Tester
Regular expressions are far easier to build incrementally than to write correctly in one attempt, which is why immediate visual feedback matters so much. Start with a literal string, then generalise one piece at a time and watch the highlighting change. This uses the JavaScript regex engine, so the syntax matches what you will get in browser and Node code — some patterns from PCRE or Python will behave differently.
Frequently asked questions
Which regex flavour is used?
JavaScript's engine, so the behaviour matches what you get in browser and Node code.
What do the flags mean?
g matches all occurrences rather than stopping at the first, i ignores case, and m makes ^ and $ match at line boundaries.
Why does my pattern match nothing?
Common causes are unescaped special characters like . ( ) [ ] and a missing global flag when you expect multiple matches.
Related free tools
- Meta Tag Generator — SEO title, description, Open Graph & Twitter tags — copy-ready.
- What Is My IP — Your public IP address, browser & device details.
- JSON Formatter — Beautify, minify and validate JSON instantly.
- Base64 Encode / Decode — Text or images ⇄ Base64 — handles huge data without freezing.
- URL Encode / Decode — Encode text for URLs or decode query strings.
- HTML Encode / Decode — Escape or unescape HTML entities.