Free Regex Tester Online
Test & Debug Regular Expressions
A free online regex tester that matches your pattern against sample text live, with matches highlighted and capture groups broken out — right in your browser. Nothing ever leaves your device.
Enter your pattern and test string
Live result 0 matches
Match details
Quick Regex Cheat Sheet
Free Online Regex Tester and Debugger
Looking for a fast regex tester online? This free tool matches your regular expression against sample text live — highlighting every match and breaking out capture groups — useful for Computer Science students learning pattern matching, and for developers debugging validation logic.
Unlike most online regex tester tools, matching here runs using your browser's native JavaScript regex engine — nothing is uploaded to a server, so it's safe to test patterns against real data.
As a completely free regex tester, there's no signup and no daily limit — type a pattern, paste your test string, and see results update instantly as you type.
Note: this tool uses JavaScript's regex engine (ECMAScript flavor). Patterns written for other engines (PCRE, Python's re, POSIX) usually work the same for common cases, but some advanced features may differ slightly.
Frequently Asked Questions
Yes — this regex tester is completely free to use, with no signup and no daily limit. Test as many patterns as you like.
No. This regex tester runs entirely in your browser using JavaScript's built-in RegExp engine — your pattern and test string are never sent to a server. That makes it safe to test against real data.
It uses JavaScript's native regex engine (the ECMAScript flavor). Most common patterns behave the same across PCRE, Python and JavaScript, but some advanced features can differ slightly between engines.
g finds all matches instead of stopping at the first one, i makes matching case-insensitive, m makes ^ and $ match the start/end of each line instead of the whole string, and s lets the dot (.) match newline characters too.
Yes — the "Match details" panel lists every match along with its position and any capture groups defined in your pattern using parentheses.
The tester shows the exact error JavaScript's regex engine reports — usually caused by unclosed brackets/parentheses, an invalid escape sequence, or an unsupported flag combination. Fix the flagged part and the error will clear automatically.