Regex Tester

About the Regex Tester

Regular expressions are powerful and famously fiddly. This tester gives you a tight feedback loop: type a pattern and instantly see what it matches, highlighted right in the text, with every capture group broken out beside it. When the pattern does what you want, copy a ready-to-run snippet for the language you're working in.

It runs entirely in your browser. Your patterns and test text never touch a server — handy when you're testing against real log lines, customer data, or anything you'd rather not paste into a random website.

What you get

• Live highlighting. Every match is highlighted in the test string, with alternating colors so adjacent matches stay readable. Hover a match to link it to its capture breakdown.
• Capture groups, side by side. Each match lists its full text plus every numbered and named group, so you can see exactly what your parentheses capture.
• A ready-made playground. The built-in sample paragraph is packed with the things people actually parse — emails, URLs, phone numbers, prices, dates, IPs, hex colors, hashtags, and versions.
• One-click pattern library. Load battle-tested patterns for email, URL, phone, date, price, IPv4, hex color, hashtag, mention, and more.
• Flags that make sense. Toggle global, ignore-case, multiline, dotall, unicode, and extended (verbose) mode and watch results update.
• Find & replace. Try a replacement using $1, $2, $& and preview the rewritten text.

Code for your language

Pick a language and the tool writes a copy-paste snippet that compiles your pattern with the right flags and iterates the matches — for JavaScript, Python, R, Java, C#/.NET, PHP, Ruby, Go, and grep (PCRE). It handles the awkward bits for you: raw strings in Python, doubled backslashes in Java and R, perl = TRUE in R, inline flags where a language has no flag argument, and the (?P<name>) vs (?<name>) named-group syntax difference between Python and the rest.

Good to know

• Matching uses your browser's JavaScript regex engine. The vast majority of everyday patterns behave identically across languages, but engines differ on advanced features — lookbehind, recursion, possessive quantifiers, and POSIX classes like [[:alpha:]] aren't all portable. The generated snippet notes per-language quirks.
• Go uses the RE2 engine, which intentionally omits backreferences and lookaround; Ruby treats ^/$ as line anchors by default and uses /m for dotall. The notes call these out.
• You can paste Python-style named groups (?P<name>…) — they're understood here and converted appropriately in each snippet.

No account, no watermark, no upload — just iterate until the pattern is right.

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