What is the Luhn algorithm?

The Luhn algorithm is a checksum formula that validates whether a card number has the correct structure. It catches most typos and transpositions but does not verify that the card account actually exists.

Can I use this to validate real customer card numbers?

Yes. The tool only performs a local checksum — no number is transmitted anywhere — making it safe to test with real card data during development.

Which card types are detected?

Visa, Mastercard, American Express, Discover, JCB, UnionPay, and Diners Club are detected from the card number prefix and length.

Validate Credit Card Numbers Online

Validating a credit card number before submitting a payment form prevents unnecessary API calls to payment processors and provides instant feedback to users. This tool validates any credit card number using the Luhn algorithm, which is the standard checksum used by all major card networks. It also detects the card type — Visa, Mastercard, American Express, Discover, and others — from the number prefix. Paste or type a card number and get immediate feedback on whether it passes the Luhn check and which network issued it. All validation runs in your browser with no network requests, making it safe for testing with real card numbers in development environments. This is useful for QA engineers testing payment forms, developers building validation logic, and anyone who needs to verify a card number format without running an API charge.

FAQ

What is the Luhn algorithm?: The Luhn algorithm is a checksum formula that validates whether a card number has the correct structure. It catches most typos and transpositions but does not verify that the card account actually exists.
Can I use this to validate real customer card numbers?: Yes. The tool only performs a local checksum — no number is transmitted anywhere — making it safe to test with real card data during development.
Which card types are detected?: Visa, Mastercard, American Express, Discover, JCB, UnionPay, and Diners Club are detected from the card number prefix and length.