Test a regular expression against your text and see matches highlighted live, with capture and named groups. Uses JavaScript regex; runs entirely in your browser.
Flags: g finds all matches (on by default here), i ignores case, m makes ^/$ match line starts/ends, s lets . match newlines. Capture groups (...) and named groups (?<name>...) are listed per match. This uses the JavaScript regex engine, so it matches what runs in the browser and Node.