Card Number Validator
Enter card numbers, one per line. Each is tested with the standard check digit formula and the length is compared with the card network it appears to belong to. Use test numbers.
Worked examples
A test Visa number
4111 1111 1111 1111
4111 1111 1111 1111: passes the check digit test, 16 digits, Visa
The check digit agrees and the prefix is Visa.
One digit changed
4111111111111112
4111 1111 1111 1112: fails the check digit test, 16 digits, Visa
The last digit was changed, so the test fails.
About Card Number Validator
This validator checks the check digit on card numbers. Enter numbers one per line and each is tested with the standard formula that card numbers follow, and the length is compared with the card network it appears to belong to.
Passing the test only shows that the number is correctly formed. It does not show that a card exists, is active or has funds. Use published test numbers, such as 4111 1111 1111 1111, when you are checking a payment form or learning how the check works.
How to use Card Number Validator
- Enter numbers, one per line. Spaces and hyphens are fine.
- Read the result for each line.
- Check the digits again for any that fail.
Common uses
- Testing a payment form with test numbers
- Learning how the check digit works
- Finding the typing mistake in a number
- Checking which network a prefix belongs to
Sources
Last reviewed 18 October 2026.
Frequently asked questions
What is the check digit test?
The last digit of a card number is worked out from the others with the Luhn formula. A single wrong digit, or two swapped digits, nearly always makes the test fail.
Does passing mean the card is real?
No. Many numbers that pass belong to no card at all. Only the card issuer can tell you whether a card is valid.
Which networks are recognised?
Visa, Mastercard, American Express, Discover, Diners Club, JCB and UnionPay, from the first digits and the length.
Where can I find test numbers?
Payment providers publish test card numbers in their developer guides. 4111 1111 1111 1111 is a widely used Visa test number.