Credit Card Number Validator

Check a card number's Luhn checksum and detect its network. Runs entirely in your browser.

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Check a Card Number
Standard Test Numbers

These are published sandbox numbers used by payment processors for testing - they are not real cards and cannot be charged.

NetworkTest Number
Visa4242 4242 4242 4242
Mastercard5555 5555 5555 4444
American Express3782 822463 10005
Discover6011 1111 1111 1117
Frequently Asked Questions

No. It only checks that the number is the correct length for its network and passes the Luhn checksum - a mathematical formula built into every card number to catch typos. It cannot tell you whether a card exists, is active, or has any funds. Only the card issuer or a payment processor can confirm that.

No. The whole check runs in your browser using JavaScript - the number you type is never transmitted anywhere or stored. That said, you should still avoid typing a real card number into any website unnecessarily; use one of the standard test numbers below instead.

The Luhn algorithm (also called the "modulus 10" check) is a simple checksum formula used to validate identification numbers, including credit and debit cards. Starting from the rightmost digit, every second digit is doubled (subtracting 9 if the result is over 9), then all the digits are summed. If the total is a multiple of 10, the number passes the check.

Visa, Mastercard, American Express, Discover, Diners Club, JCB and UnionPay, based on each network's published numbering ranges (IIN/BIN prefixes) and card length.

Yes - that is exactly what it is for. Use well-known sandbox numbers like 4242 4242 4242 4242 (Visa) or 5555 5555 5555 4444 (Mastercard), which are published by payment processors specifically for testing, so you can confirm your form's validation logic without risking a real card.
How It Works
  • 1. Network detected from the card number's prefix
  • 2. Length checked against that network's rules
  • 3. Luhn checksum verified digit-by-digit
  • 4. Overall format validity shown
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