Live Regex Tester, Highlighter & Cheat Sheet
Test regular expressions in real time with capture group breakdowns, replace preview & preset library.
๐ 100% Local Browser Execution โ Files never leave your device โ No email ยท No sign-up ยท No watermark ยท Free
Quick Presets:
Test Text 0 matches
Live Highlighted Matches Capture Groups & Match Breakdown Replacement Output Preview
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How to Use Live Regex Tester, Highlighter & Cheat Sheet
- Enter your regular expression pattern and flags (g, i, m, s, u) at the top โ or click one of the built-in presets (UK Postcode, Email, IPv4, URL, ISO Date, Password).
- Type or paste your test string below to see every match highlighted in real time alongside a detailed table of numbered and named capture groups.
- Use the Replace tab to preview string substitutions ($1, $2, $<name>) and copy a ready-to-use JavaScript, Python, or Go code snippet.
Real-Time Regular Expression Debugging Without Lag
Writing and verifying regular expressions shouldn't require guesswork. Shoal's Live Regex Tester evaluates patterns instantaneously in your browser, visualising every full match, numbered group ($1, $2), named capture group ((?<name>...)), and character index range.
Built-In UK & Global Validation Patterns
Includes battle-tested one-click patterns for UK Postcodes (BS 7666 standard), UK mobile/landline numbers, RFC-5322 email addresses, semantic version strings, hexadecimal colours, and Markdown links.