Regex Tester is a 100% free, browser-based utility that enables you to test regular expressions with live match highlighting. Unlike traditional cloud converters, all processing executes locally on your device with zero server uploads, delivering immediate results and ironclad data privacy.
About the Regex Tester
The Regex Tester lets you write a regular expression and instantly see every match highlighted in your test text. A table lists each match with its position, numbered capture groups and named groups, so you can check exactly what your pattern captures.
Toggle flags such as global, case-insensitive, multiline, dotAll and unicode, try a replacement string with $1 or $<name> references, or start from a preset for emails, URLs, IP addresses and dates. It uses the same JavaScript RegExp engine as your browser and Node.js.
How to use the Regex Tester
- Enter your regular expression in the pattern field (without surrounding slashes).
- Choose the flags you need, such as g (global) or i (ignore case).
- Paste test text and review the highlighted matches and the match table.
- Optionally enter a replacement to preview the result of String.replace.
Features
- Live match highlighting
- Capture & named groups table
- Replace preview with $1 / $<name>
- Presets for common patterns
Why Choose In-Browser Regex Tester vs Cloud Converters?
| Feature | Toolora (In-Browser) | Traditional Cloud Tools |
|---|---|---|
| Data Privacy | 100% Private (Files stay on device) | Uploaded to remote servers |
| File Size Limits | Unlimited (Limited only by your RAM) | Restricted (e.g. 10MB–50MB caps) |
| Processing Speed | Instant (Zero upload/download delay) | Slow upload & queue waiting |
| Ads & Popups | Clean, distraction-free | Heavy banner & interstitial ads |
Frequently asked questions
Which regex flavour does this tester use?
It uses the JavaScript (ECMAScript) RegExp engine built into your browser, so results match what you get in JavaScript, TypeScript and Node.js. Other flavours such as PCRE or Python are very similar but have some differences, for example in lookbehind and possessive quantifiers.
Why does my pattern only find one match?
Without the g (global) flag a regular expression stops after the first match. Enable the global flag to find every match in the text.
How do I reference a named group in the replacement?
Define the group with (?<name>...) and use $<name> in the replacement string. Numbered groups are referenced with $1, $2 and so on, and $& inserts the whole match.