Regex Tester
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What is a regex tester?
A regex tester lets you write a regular expression and immediately see which parts of a sample string it matches, without switching to your code editor and running it. This tool highlights every match live and breaks out capture groups so you can debug complex patterns quickly.
When would I use this?
- Validating an input format, like an email or phone number pattern, before adding it to your code.
- Debugging why a regex isn't matching what you expect in a script or config.
- Extracting structured data from log lines or text using capture groups.
How it works
Matching uses your browser's native JavaScript regex engine, so behavior matches exactly what you'd get in the browser console or Node.js. Nothing you type is sent anywhere.
Frequently asked questions
It uses your browser's native JavaScript regex engine (ECMAScript), the same engine used in Node.js and every modern browser. Supports common flags: g, i, m, s, u, and y.
No. Matching runs entirely client-side in JavaScript. Neither your pattern nor your test string is transmitted or stored.
Yes. Each match is broken down with its full match text and any numbered or named capture groups, updated live as you type.
Common causes: missing the "g" flag (only the first match will highlight without it), unescaped special characters like . or (, or a typo in a character class. Check the live match count as you edit.