Test Data Generator
Generate names, emails, usernames, UUIDs, IP and MAC addresses, Luhn-valid card numbers and more — seeded so the same seed always yields the same rows, entirely in your browser.
Also available as a desktop app for Windows.
About this tool
Test data has a property almost every random generator throws away: it has to be reproducible. A bug that only shows up with a specific row of the 20 you pasted yesterday is worthless if those 20 rows are gone forever. So this tool is built around a seed: the same seed with the same fields produces exactly the same rows — today, next month, on your machine and on your colleague’s. Write the seed into the bug report ("checkout-bug-47") and anyone can regenerate the evidence.
Every format is locked to its public standard rather than to "looks about right". UUIDs are version 4 with the correct version and variant bits (RFC 9562). Card numbers pass the Luhn checksum (ISO/IEC 7812-1) so they survive form validation, yet correspond to no real issuer range. Emails use the domains RFC 2606 reserves for documentation, so test mail can never be delivered to anyone. Country codes are ISO 3166-1 alpha-2, IP addresses avoid the network and broadcast addresses of each /24, and MAC addresses carry the unicast bit set correctly.
Everything runs in your browser. There is no server, no request and no logging — the rows are produced by plain arithmetic on the seed, which is also why it works with the network switched off and why the same seed cannot help but give the same answer.
Frequently asked questions
- What exactly does the seed control?
- Everything. Each generated value is a pure function of the seed and its position in the sequence. Change the seed and every row changes; keep it and you can regenerate the identical table forever. An empty seed picks a fresh random one each session and shows you which number it used, so even "I did not care about the seed" is reproducible.
- Are the card numbers dangerous?
- No. They satisfy the Luhn checksum, which is a 1954 arithmetic test over the digits themselves — it says nothing about whether an account exists. The generated numbers start with 4 but are not inside any real issuer’s allocated range and cannot be charged. They exist so a payment form’s format validation can be exercised end to end.
- Why do generated emails use reserved example domains?
- RFC 2606 sets aside a block of example domains for documentation and testing, so mail sent to them can never reach a real inbox. A generator that emits addresses at a live consumer mail provider is not producing test data — it is producing misdirected mail and the occasional very confused recipient.
- How random are the passwords?
- Each password is 14 characters and guaranteed to contain at least one lowercase letter, one uppercase letter, one digit and one symbol, with the rest drawn uniformly from the combined pool and the whole string shuffled. They are generated from the seed, which means they are only as secret as the seed — fine for filling a signup form in a test run, never for real accounts.
- Does this send my data anywhere?
- No. Generation is plain arithmetic in the page — there is no server, no request and no telemetry, and the tool keeps working with the network switched off. The clipboard buttons write directly from the page to your clipboard.