AI Regex Generator

The AI Regex Generator writes regular expressions from plain English and tests them before you see them. Describe what to match, choose JavaScript, Python, PCRE, PHP, Java or Go, add a few examples if you have them, and get a pattern with every part explained, a list of passing tests, a live tester and code to paste.

Why it's different

• Tested, not guessed. The pattern is run against strings that should match and strings that shouldn't. If a test fails, it's fixed automatically and you see every result.
• Your examples count. Add strings that must or must not match and they become tests.
• Right for your language. Flavor limits are checked, such as no lookarounds in Go.
• Safe to use. Patterns that can hang on long input are flagged.
• Explained. Every token of the pattern is described in plain words.

How to create a regex

1. Describe what to match, e.g. "UK postcodes, case-insensitive".
2. Choose the flavor and options, and add examples that must and must not match.
3. Click Generate regex, check the tests, try it in the live tester and copy the code.

Regex tips

• Be specific about the edges. Say what should not match, too.
• Anchor when validating. Use Match the whole string for form validation, so extra text isn't allowed.
• Prefer simple patterns. A readable pattern is easier to fix later.

Related tools

Write database queries with the AI SQL Query Generator.

Frequently asked questions

How do I write a regular expression?

Describe what you want to match in plain words, choose the language you'll use it in, and add a few strings that must and must not match. The generator writes the pattern, tests it against those strings and more edge cases, fixes it if a test fails, and explains every part.

Can I trust an AI-generated regex?

Only as far as it's tested, which is why every pattern here is run against examples before you see it: your own and edge cases for what should and shouldn't match. Each test is shown with its result, and you can test the pattern on your own text in the live tester.

Does the regex work in Python, JavaScript and other languages?

Choose your flavor and the pattern is written for it: for example no lookarounds or backreferences for Go (RE2), and (?P<name>) named groups for Python. The code tab shows how to use it in JavaScript, Python, PHP, Java and Go.

What is catastrophic backtracking?

Some patterns, usually with nested repetition like (a+)+, can take an extremely long time on input that almost matches. The generator warns you when a pattern has that shape, so you can simplify it before using it on user input.

The regex doesn't match something it should. What now?

Type the string under Should also match (or Should not match) and click Fix the pattern. It's added to the tests and the pattern is rewritten until they pass.

Is it free?

Yes. Every day you get free AI runs, and each run gives a tested, explained pattern. The live tester, the code snippets and the examples on this page are always free. Fixing a pattern with more examples uses one run.