AI Regex Generator

Describe It in Plain English, Get a Working Regex Back

Writing a regular expression from scratch means remembering the difference between a lazy and greedy quantifier, whether you need a non-capturing group, and how to escape a literal dot — every time. This tool skips that: describe what you want to match in plain English ("a US phone number like (555) 123-4567," "a hex color code," "a strong password with at least one number and symbol") and it generates a working JavaScript-flavored regex, explains how it works, and gives you example strings that should and shouldn't match — plus a live tester right on the page so you can paste your own text and see it highlighted immediately.

How to use it

• Type a plain-English description of the pattern you need — be as specific as you can about the format (e.g. "5-digit US zip code, optionally with a 4-digit extension" beats just "zip code").
• Click Generate and you'll get the regex pattern, its flags, and a short explanation of what each part does.
• Check the example matches and non-matches to sanity-check the pattern against what you actually intended.
• Paste your own real text into the tester box below to see live highlighted matches before you copy the pattern into your code.

Real-world use cases

Generating a form validation pattern for emails, phone numbers, or postal codes without digging through Stack Overflow, building a quick pattern to find and replace a specific format across a text file or spreadsheet, learning how a particular kind of regex is actually constructed by reading the plain-English explanation, or double-checking that a pattern you found online actually matches the edge cases you care about.

Frequently asked questions

What regex flavor does this generate?

JavaScript-flavored regular expressions — the same syntax used by browsers, Node.js, and most modern web frameworks. Most of the syntax overlaps with other flavors like PCRE (used in PHP and Python), but a few features like lookbehind support can differ, so double-check if you're pasting the pattern into a different language.

Why does the generated pattern sometimes look more complicated than I expected?

Real-world formats usually have more edge cases than they first appear — an "email address" pattern that only matches the happy path will reject valid addresses with plus-signs or subdomains. The AI aims for a pattern that handles common real variations, not just the simplest possible case.

What if the generated pattern doesn't match what I actually meant?

Rephrase your description with more specific detail — mention the exact format, give a concrete example inline, and call out any edge cases you care about (optional parts, case sensitivity, length limits). The example matches and non-matches are there specifically so you can catch a misunderstanding before you use the pattern anywhere important.

Is there a limit to how many patterns I can generate?

Yes, a modest per-minute and per-day limit to keep the tool available for everyone — if you hit it, just wait a minute and try again.

Does the live tester run the pattern on a server somewhere?

No — once the pattern is generated, the tester runs entirely in your browser using JavaScript's built-in regex engine. Nothing you paste into the test box is sent anywhere.