Regex Tester
Enterprise safeReal-time regex debugger with match highlighting and capture groups.
Frequently asked questions
What regex flavor does this use?
Your browser's native JavaScript RegExp engine — the same one that will run your pattern in production if you're testing it for a JS/TS project. It is not PCRE, so a few advanced constructs (recursion, atomic groups) aren't supported.
Can a bad pattern freeze the page?
No. Every match runs inside a Web Worker with a 2-second hard timeout, sandboxed away from the page you're looking at. If a pattern catastrophically backtracks, the worker is killed and restarted automatically — your tab stays responsive.
Does it explain what my pattern means?
Yes — the token-by-token breakdown describes each part of the pattern in plain language (character classes, quantifiers, groups, anchors) so you can sanity-check a regex you inherited or forgot the details of.
Is my test text uploaded anywhere?
No. Both the pattern and the text you're matching against stay in your browser tab; only the match results are computed by the sandboxed worker.
About this tool
Test a JavaScript regular expression against sample text and inspect matches, capture groups, and a plain-language pattern breakdown.
Workflow
- Enter the pattern and select the flags used by the target JavaScript code.
- Add representative text, including edge cases that should not match.
- Review highlighted matches and capture groups as the pattern changes.
- Copy the final pattern into a real test suite before shipping it.
Things to know
- The engine follows browser-native JavaScript RegExp behavior, not PCRE or another flavor.
- A worker timeout protects the page from patterns that backtrack excessively.
- A passing sample is not proof that a pattern handles every production input.
Regex Tester on devsutils.com — Real-time regex debugger with match highlighting and capture groups. It runs entirely in your browser: the input you paste is processed by client-side JavaScript and is never uploaded, logged, or stored. devsutils.com is a privacy-first suite of 70 developer utilities — JSON formatter, JWT decoder, Base64 encoder, regex tester, UUID generator, hash generator and more — with no accounts and no server-side processing.