Regex Tester

Build and debug regular expressions with live highlighting, numbered and named groups, and protection against unsafe HTML injection.

Developer Tools Utilities Runs locally No sign-up

Regex tester

Live matching

Pattern

Flags

Without g, only the first match is returned. Sticky mode requires each match to start where the previous one ended.

Test text

Limit: 100,000 characters and 2,000 matches. Matching runs in a worker that is stopped after 250 ms; if workers are unavailable, patterns with nested quantifiers such as (a+)+ are refused before they can freeze the page. An empty pattern is rejected.

Highlighted matches

Matches 0

Captures 0

Time 0.0 ms

Examples

Highlights are built from DOM text nodes, not HTML, so test text cannot inject markup. Zero-length matches are highlighted invisibly and advance the search position safely.

About Regex Tester

Test regular expressions with live matches, capture groups, flags, and safe highlighted output.

This tool runs locally in your browser. It does not upload your input, require an account, or store your data on a server. If a feature needs a network request, the interface asks before sending anything.