Credit Card Validator & Luhn Checker
Check card-number length, network format and Luhn checksum in your browser. Format validation does not confirm a real card, balance or payment approval.
Check a card number’s format.
Check the network, number length and Luhn checksum. Your input stays in this browser and does not use your generation allowance.
Recognizes seven supported networks. Unknown prefixes are not proof of an invalid card. This does not verify an account, issuer, cardholder, expiry, security code or payment capability.
Read each card-format check independently.
This validator checks a number’s supported network pattern, length and Luhn checksum in your browser. It is useful for debugging a card-input component before integrating a payment provider. Read the individual checks instead of treating a single passing indicator as evidence of a working payment card.
- 01
Use a synthetic sample
Copy a generated test value or a provider-documented sandbox example. Real customer card details are unnecessary for a format test.
- 02
Inspect each check
A number may satisfy Luhn but have an unsupported prefix or length. Record the specific condition that passed or failed.
- 03
Change one property
Remove a digit or alter the final digit and repeat the check. This makes a regression fixture easier to interpret than several simultaneous changes.
Example: isolate a checksum failure
Baseline: a generated sample that passes format checks
Mutation: change only the final digit
Expected: checksum check fails; original prefix remainsThe comparison helps distinguish checksum behavior from network detection. Save the original and changed strings with their expected outcomes.
| Check | Question answered | Question not answered |
|---|---|---|
| Network | Does a supported pattern match? | Who owns the account? |
| Length | Is the digit count supported? | Is the account open? |
| Luhn | Is the checksum consistent? | Will payment be approved? |
Before you use the result
Practical answers for your next test.
Can this validate a security code?
A number-only format check cannot establish whether a security code belongs to an account.
Why does a made-up number pass?
The checks describe structure and mathematics. Synthetic samples can deliberately satisfy both.
Are inputs sent to a payment network?
No. This tool performs its card-format checks in your browser; it does not request issuer authorization.