Regex Tester

The Regex Tester lets you build, test and debug JavaScript regular expressions against sample input in real time. Highlights every match, shows capture groups, supports all standard flags (g, i, m, s, u, y), and explains what your pattern matches step by step. Ideal for quick pattern checks, learning regex syntax, or debugging a complex expression that's misbehaving in production code.

Every developer has spent an afternoon debugging a regex that 'looks right' but doesn't match what they expect — usually because of greedy vs lazy quantifiers, unescaped special characters, or overlooked whitespace. A visual tester with instant feedback is the fastest way to converge on the correct pattern.

Because the tester runs your regex in the browser's JavaScript engine, the behavior matches exactly what you'll see in Node.js, browser JavaScript and Deno. Pattern syntax follows ECMAScript spec — if you need to test Perl, Python or PCRE regexes, be aware some features (like recursive patterns and named backrefs) differ.