Enter a pattern and toggle flags like g, i and m, then type test text to see matches highlighted, capture groups listed, and an optional replacement preview.
g finds all matches, i makes matching case-insensitive, and m lets ^ and $ match at line boundaries instead of only the whole string.
Parentheses in a pattern capture parts of each match so you can extract or reference them, e.g. (\d{4}) captures a four-digit year.
The JavaScript RegExp engine, so syntax matches what runs in browsers and Node.js, including named groups and lookaheads.