Code

Build regex patterns without the headache

Describe what you need to match and get a correct regular expression with an explanation.

For the best results: Describe the pattern to match in plain English. Example: "Match all email addresses" or "Extract phone numbers from text, with or without country code."

AI can make mistakes. Check important information before relying on it.

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What is Regex Generator?

Regex Generator is a free AI coding assistant that turns a description of what you need to match into a correct regular expression with an explanation. Each request is handed to a code-specialized model chosen for the task, returning the pattern in a code block, an explanation of what each part matches, a set of example strings that do and don't match so you can sanity-check it, and a note flagging where the syntax differs between languages such as JavaScript and Python in seconds. You paste and go, with no login and nothing to install, and the code you share is not retained once the session ends.

✦Paste code and go, no login, nothing to install
✦Code-specialized models are selected per request automatically
✦Your code is not retained after the session ends

Models: It routes across strong coding models including Llama, Gemini and Mistral families, picking the best available one per request. The exact model used is shown after every response.

See it in action

A developer needs a UK postcode validation pattern for a signup form running in JavaScript.

What you type

I need a regex to validate UK postcodes in a signup form, like 'SW1A 1AA' or 'BS1 5TR'. It runs in JavaScript.

What you get

Pattern: /^[A-Z]{1,2}\d[A-Z\d]? \d[A-Z]{2}$/i Explanation: one or two letters, a digit, an optional letter or digit, a space, then a digit and two letters. Matches: "SW1A 1AA", "BS1 5TR", "M1 1AE". Doesn't match: "BS15TR" (no space), "123 4AA" (starts with digits). Language note: written for JavaScript; the /i flag makes it case-insensitive.

Tip: The list of matching and non-matching examples is the tool checking its own work. If one of your must-reject cases isn't in that list, paste it back and ask it to prove the pattern rejects it, because that is exactly where a pattern quietly lets bad input through.

Use cases

What people use it for

Match Australian phone numbers in a customer export without an hour of trial and error.

Build the validation pattern for a signup form's password rules in a single request.

Extract timestamps from server logs so you can isolate the slow requests.

Who uses Regex Generator?

Log wranglers

building a pattern to pull timestamps, IPs or error codes out of server logs for a quick grep or filter

Spreadsheet users

writing a find-and-replace pattern to clean thousands of cells at once in their editor regex search

Form developers

generating a validation pattern for emails, phone numbers or postcodes and getting the explanation to check the edge cases

How it works

1Paste your code or describe what you need built.
2A code-specialized model writes, fixes, or explains it.
3Copy the code out, or ask follow-ups to iterate on it.

Tips for the best results

Give three or four real examples of strings that should match and, just as importantly, a couple that should not, so the pattern is tuned to your actual data.
Name the tool or language you will run it in, whether JavaScript, Python, PCRE, grep or your editor, because escaping and supported features vary between them.
Say whether matching should be case-sensitive and whether it must anchor to the whole string or just find a substring, as these change the pattern significantly.
Do not ask regex to parse deeply nested structures like HTML or balanced brackets; use a real parser and reserve regex for flat, predictable patterns.
Always test the returned pattern against your edge cases in a live regex tester before shipping it, since a small quantifier change can match far more than you intended.

FAQ

Frequently asked questions

Do regex flavors matter, and which one will I get?

They matter more than people expect, lookbehind, named groups and unicode handling differ between JavaScript, PCRE, Python and Go. Say where the pattern will run and you'll get one valid for that engine. A pattern that works in one tester can quietly fail in another environment.

What's the best way to describe the pattern I need?

Give examples, not just rules. A handful of strings that should match and a few that shouldn't pins down your intent far better than prose alone. Edge cases you mention explicitly (optional country codes, trailing whitespace, mixed case) are the edge cases the pattern will actually handle.

Will I understand the pattern I get back?

Each pattern arrives with a breakdown of what every piece does, which is worth reading even when the regex works first go. Understanding the parts means you can adjust it yourself next month instead of starting again, and regex knowledge compounds quickly once patterns stop looking like line noise.

How should I test a generated regex before using it?

Run it against real data, not just the examples you supplied, a log file, a column export, whatever it will face in production. Watch for the classic failure modes: patterns that match too greedily, and edge cases like empty strings or unicode. A minute of testing beats a subtle production bug.

Can regex parse HTML or nested brackets?

Not reliably, and no generator changes that, regular expressions fundamentally can't track arbitrary nesting. Ask for one anyway and you'll be told when a parser is the better tool for the job. For quick extraction from predictable, flat snippets regex is fine; for real HTML structure, use an HTML parser.

Is this regex generator free to use?

Yes, free with no sign-up, account or payment. Describe what you want to match and get a working pattern plus an explanation. There is no cap tied to a plan. The pattern is generated from your description; you test it against your own text to confirm it matches what you expect.

Can it explain an existing regex I already have?

Yes. Paste a pattern you did not write and it breaks it into tokens, describing what each group, quantifier and character class does and what a sample match looks like. This is often faster than decoding a cryptic one-liner by hand, and it helps you see why a pattern matches too much.

Does it give me the replacement string for find and replace?

Yes. Ask for a substitution and you get both the search pattern and the replacement, using the right back-reference syntax such as the dollar-one group. Say where you are running it, since editors, sed and programming languages differ on how capture groups are referenced in the replacement.

What are the usage limits?

Code tools are text tools, so they are unmetered during the current free launch phase, iterate on a bug or generate as many drafts as the work needs. A short per-minute limit guards against scripted abuse only. Paid plans with higher limits and priority model access are coming soon.

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