Regex Tester

This tool uses JavaScript's native RegExp engine, the same syntax used in Node.js, browsers, and most modern web frameworks. It supports lookaheads, lookbehinds, named capture groups, and all standard JavaScript regex features.

g (global) finds all matches, not just the first. i (ignore case) makes matching case-insensitive. m (multiline) makes ^ and $ match line boundaries. s (dotAll) lets . match newline characters. u (unicode) enables full Unicode support. y (sticky) matches only at the lastIndex position.

No. All regex testing happens entirely in your browser. Your patterns and test strings never leave your device, making this safe for proprietary code, API payloads, and sensitive data.

Parentheses in your pattern create capture groups. Numbered groups appear as $1, $2 in replacements. Named groups use (?<name>...) syntax and appear in the groups table. Each match shows its full substring plus every captured group value.

Common issues include missing the global (g) flag when testing multiple matches, unescaped special characters like . or *, or anchors (^ $) behaving differently without the multiline (m) flag. Check the error message for syntax problems, or try a common pattern from the reference panel.