Credit Card Validator

Validate credit card numbers using the Luhn algorithm and detect card type

What is it and how does it work?

Credit card number validation uses the Luhn algorithm (also called modulus 10) — a simple checksum formula that detects single-digit errors and most transposition errors. When you enter a card number in a checkout form, the browser can validate it client-side using Luhn before even sending it to the server. This tool also identifies the card network (Visa, Mastercard, American Express, Discover, etc.) from the card number prefix (IIN/BIN), and shows the expected number length and CVV digit count for that network.

This tool is useful for developers testing payment integrations — generating valid-format test card numbers that pass Luhn without using real card data. It also helps identify why a card number fails validation: wrong length, wrong prefix for the claimed network, or Luhn checksum failure. Note: a number passing Luhn is structurally valid but is not a guarantee the account exists, is funded, or hasn't been cancelled.

Common use cases

• Payment form testing: generate a Luhn-valid Visa test number (starting with 4) to use in development/staging environments without needing a real card.
• Input validation debugging: a user reports their card is being rejected — paste the number to check if it passes Luhn and matches the expected format for their network.
• Network identification: paste a card number prefix (first 6 digits, the BIN) to identify which bank and card network issued it.

Frequently asked questions

What is the Luhn algorithm?

Starting from the rightmost digit, double every second digit. If doubling produces a number > 9, subtract 9. Sum all digits. If the total modulo 10 is 0, the number is valid. Example: 4111 1111 1111 1111 (Visa test card) produces a sum of 60 → 60 mod 10 = 0 ✓.

Does a Luhn-valid number mean the card exists?

No. Luhn only verifies the structure of the number, not whether an account actually exists. A random 16-digit number that happens to pass Luhn is structurally valid but almost certainly not a real account. Real card validation requires authorisation through the payment network.

What are BIN/IIN numbers?

The Bank Identification Number (BIN, also called Issuer Identification Number/IIN) is the first 6–8 digits of a card number. They identify the network (Visa=4, Mastercard=51–55, Amex=34/37, Discover=6011/65) and the issuing bank. BIN lookups can reveal the card's country of issue and card type (debit/credit).

Is it safe to use real card numbers in this tool?

This tool runs entirely in your browser — no data is sent to a server. However, it's best practice never to use real card numbers in any test or debugging tool unless absolutely necessary. Use the test card numbers provided by your payment processor (Stripe, Braintree, etc.) instead.

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