Regex Tester

Regex Tester runs a regular expression against your own sample text and highlights exactly what it matches, character by character, the moment you stop typing. You put your pattern in the regex field at the top, flip on the flags you need, and drop your test string into the box below. Matches light up inline, and a results panel splits each one into its capture groups, its named groups, and its start and end indices, so you can prove the pattern does what you think before you trust it. The engine is the browser's own JavaScript RegExp, which means the exact syntax you validate here pastes straight into Node.js, a React component, or a `String.replace` call with no dialect surprises. Everything happens client-side in your tab. Your pattern and your test data are never uploaded, stored, or logged, which matters when the text you are matching against is a batch of real emails, production log lines, leaked API keys you are scrubbing, or customer records. The situations that send people here are concrete: checking whether an email or phone-validation pattern accepts the awkward inputs (plus-addressing, `+` country codes, unusual TLDs) instead of only the tidy ones; pulling timestamps and status codes out of log files; drafting a find-and-replace before you unleash it on a whole repo; or working out why a greedy `.*` is swallowing three fields instead of one. The `g` flag switches you from first-match to every-match, `i` spares you from writing `[Aa][Bb]` by hand, and `m` changes where `^` and `$` land on multi-line input. Backend developers, QA engineers, and data analysts who live in `grep`, `sed`, or an editor's search box all end up building patterns faster here. One habit pays off: build incrementally, add a single group at a time, and watch the group breakdown so a stray unescaped parenthesis becomes an obvious extra capture rather than a bug you ship. Seeing matches update live turns regex from guess-and-rerun into something you can actually read.