Regex Tester & Debugger
Free online regex tester and debugger — build and test regular expressions with live match highlighting, an auto-generated explanation, match information, a quick reference, substitution and a multi-language code generator. Supports JavaScript, PCRE2, Go and Rust, entirely in your browser.
Character classes
Anchors
Quantifiers
Groups & references
Lookaround
Escapes & meta
Unicode & POSIX
Flags / modifiers
Runs entirely in your browser — nothing you enter is uploaded or stored.
A private, in-browser regex tester and debugger
Build, test and debug regular expressions with live match highlighting, an auto-generated explanation of every token, full match information (numbered and named groups with their positions), a searchable quick reference, substitution and list output, and a code generator for JavaScript, Python, PHP, Go, Java, C#, Rust and Ruby.
Unlike server-based testers, everything here runs locally in your browser — the JavaScript flavor on the native engine and PCRE2, Go and Rust on real engines compiled to WebAssembly. Your pattern and test text are never uploaded, saved patterns stay private on your device, and there are no ads or quotas.
Frequently asked questions
Which regex flavors are supported?
JavaScript runs on your browser native engine; PCRE2 (PHP), Go (RE2) and Rust run on real engines compiled to WebAssembly that load on demand. Every flavor executes locally — your pattern and test text are never uploaded.
How is this different from regex101?
Same core workflow — live match highlighting, an auto-generated explanation, match information, a quick reference, substitution, list output and a code generator for many languages. The difference is privacy: everything runs in your browser, so there are no ads, no quotas, and saved patterns stay private on your device. You can verify it in the Network tab or our Content-Security-Policy.
Are my saved patterns private?
Yes. Saved patterns live in your browser localStorage only — they are never sent to a server. Clearing your browser data removes them. Use the Share button to copy a link that encodes the pattern and test string in the URL if you want to share one.
Does the explanation support every token?
The explanation panel parses character classes, quantifiers, groups (capturing, named, non-capturing, atomic), lookaround, anchors, backreferences, Unicode properties and escapes, and annotates each with a plain-English description.