About this tool
RegexCheck runs your pattern with the same JavaScript engine your code ships to — what matches here matches in Node.js and every browser. Matches highlight as you type, capture groups are listed per match, and the breakdown table translates each piece of the pattern into plain language.
Patterns run inside a Web Worker with a 2-second kill switch, so a catastrophically backtracking regex like (a+)+$ cannot freeze the page. Everything stays on your machine — the text you paste is never uploaded. Need a starting point? Grab a ready-made email, URL or IP pattern, or keep the cheatsheet open. More free tools at dec0de.dev.