Regex Tester

This tool uses the browser's native JavaScript RegExp engine. It supports all standard JS regex syntax: character classes, quantifiers, anchors, lookaheads, lookbehinds (ES2018+), named capture groups (?<name>...), and Unicode property escapes with the u flag.

The five flags modify how matching works: g (global) finds all matches instead of just the first; i makes matching case-insensitive; m makes ^ and $ match start/end of each line; s makes the dot (.) match newlines too; u enables full Unicode support.

Check that the g (global) flag is enabled — without it, only the first match is highlighted. Also verify your pattern is valid (no red border on the input) and that the test string actually contains text that fits your pattern.

Capture groups are parts of a regex pattern wrapped in parentheses — e.g. (\d{4}). They let you extract specific portions of a match. Named groups use the syntax (?<year>\d{4}). The Groups tab shows each captured value separately for every match.

No. This tool runs entirely in your browser using the native JavaScript RegExp engine. Your pattern and test string are never sent to any server. You can safely test sensitive data patterns — though we recommend using dummy data as a best practice.

Greedy quantifiers (*, +, {n,m}) match as much text as possible. Lazy quantifiers (*?, +?, {n,m}?) match as little as possible by adding a ? after. For example, <.+> matches an entire line of HTML tags greedily, while <.+?> matches each individual tag.