Regex Tester
Test a JavaScript regular expression against sample text: see every match, its position, capture groups, and a replacement preview.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
How it works
Uses the browser's own JavaScript RegExp engine (ECMAScript syntax). Flags: g global, i ignore case, m multiline, s dotAll, u unicode, y sticky, d indices. Without g only the first match is shown. The replacement field uses JavaScript replacement syntax ($1, $<name>, $&). Setting d also shows the position of each capture group. Matching runs on your CPU in a background worker and is stopped after 1.5 seconds, so a pathological pattern cannot freeze the page. Where that worker cannot be started, the tool reports that safe execution is unavailable and runs nothing, rather than evaluating your pattern on the page itself. Test text is capped at 200,000 characters and 2,000 matches.