Regex Tester
Test JavaScript regular expressions with flags, capture groups, replacement preview and safety warnings.
About, use cases, and privacy
About Regex Tester
A regex tester helps you verify a pattern against real sample text before putting it into code, validation rules, scraping scripts, log filters, or search pipelines. Regular expressions are compact but easy to get wrong, especially around escaping, word boundaries, grouping, and greedy matches.
This tool uses JavaScript regular expressions, supports flags on the second line, lists capture groups, and can show a simple replacement preview with a replace: line. It also stops very large match sets so a bad pattern does not freeze the page.
Use it for form validation, route matching, text extraction, log inspection, and QA examples. Always test edge cases, empty strings, Unicode text, and inputs that should not match.
Guides for this tool
Regex Cheat Sheet for JavaScript Developers
A practical JavaScript regex cheat sheet with anchors, groups, quantifiers, character classes and testing advice.
Regex Email Validation Examples
Practical email regex examples, tradeoffs and safer validation patterns for JavaScript forms.
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Frequently Asked Questions
It uses JavaScript regular expressions in the browser.