What regex flavor does this use?

This uses JavaScript regular expressions (ECMAScript flavor), which is the same as what runs in browsers and Node.js.

Can I use flags like global and case-insensitive?

Yes. You can add flags (g, i, m, s, u) to your pattern. The global flag (g) is enabled by default to show all matches.

What are capture groups?

Capture groups (defined with parentheses) extract specific parts of a match. For example, (\d{4})-(\d{2}) captures year and month separately from a date string.

Regex Tester

Pattern Tools

Test regular expressions with live highlighting and capture groups

By DevToolHQ teamUpdated 2026-04-15100% client-sideMethodology

100% client-side processing

Regex Pattern

Flags

Test String

About Regex Tester

Tests regular expressions against input text with real-time match highlighting. As you type either the pattern or the test string, matches are highlighted inline. Capture groups are extracted and displayed separately, showing the matched content for each numbered and named group. This uses JavaScript's ECMAScript regex flavor — the same engine that runs in browsers and Node.js. Common flags are supported: g (find all matches, not just the first), i (case-insensitive), m (multiline, making ^ and $ match line boundaries), and s (dotall, making . match newlines). The tool defaults to the global flag. Beyond simple match/no-match testing, seeing capture groups in isolation is the most useful feature for complex patterns. A pattern like (\d{4})-(\d{2})-(\d{2}) on a date string will show group 1 as the year, group 2 as the month, group 3 as the day — immediately confirming your pattern is capturing what you intend. Named groups ((?<year>\d{4})) display with their names rather than numbers. The built-in pattern library covers the most-requested patterns: email, URL, IPv4, phone number, credit card, postal code — useful as a starting point or sanity check against your own patterns.