Frequently asked.

What is regexguide.com?

A free, in-browser regex explainer and pattern library. Paste any regex, get a plain-English breakdown. No signup, no upload, no tracking of your regex content.

How is it different from regex101.com?

regex101 is built around testing regex against strings. regexguide.com is built around understanding what a regex does. Both have their place. If you wrote the regex yourself and want to verify it matches, regex101 is excellent. If someone else wrote it and you want to know what it means, we're better.

Which regex flavors does the explainer support?

The explainer currently supports the JavaScript regex flavor in full. PCRE, Python, Go, Java, .NET, and Rust support is planned and will be added incrementally. Most regex features are common across flavors, so the explanation will be substantially correct for any of them — but the specific language flavor matters for edge cases like lookbehind support, named-group syntax, and Unicode handling.

Is my regex sent to a server?

No. The parser and explainer run entirely in your browser using JavaScript. You can verify this by opening your browser's Network panel before typing — no outbound requests carrying your regex will appear.

What about the patterns in the library — are they safe to copy?

Each pattern in our library has been hand-curated and tested against pass/fail examples. We document known edge cases on each pattern's detail page. That said, regex is famously context-dependent. Always test a pattern against your own real data before relying on it in production.

Why no AI features?

Existing AI regex tools (autoregex.xyz, several "AI regex generator" sites) produce patterns that look plausible but are often subtly wrong. The cost of a wrong regex in production code is high — data loss, security holes, broken validation. We've intentionally built regexguide.com as the human-curated alternative. Every pattern in our library is verified by a human against multiple test cases.

Can I save my regex to my account?

There are no accounts. Use your browser's bookmark feature, or copy the URL — patterns from the library link directly to a pre-filled explainer.

Does it work on mobile?

Yes. The site is designed mobile-first and works on phones and tablets. Long, complex regexes are easier to read on a wider screen but the core functionality is fully available on mobile.

How is the site funded?

Ads. We use Google AdSense and Adsterra to keep the site free. They show banner ads and may use cookies to personalize them. See the privacy policy for opt-out instructions.

Is there a cheat sheet PDF?

Yes — download here. Single-page reference of every regex token, character class, group construct, and flag. Print it, pin it, never Google "regex word boundary" again.

I found a bug / wrong explanation / broken pattern

Please tell us via the contact page. Bug reports about explainer accuracy or library correctness are the most valuable feedback we can receive.