Credit Card Validator
Luhn checksum + issuing network detection
Card number
About
Check whether a credit card number passes the Luhn checksum and identify the issuing network from its prefix and length. The check runs entirely in your browser — the number is never sent anywhere. Useful for validating form input or learning how card numbers are structured.
Examples
Validate a Visa number
4111 1111 1111 1111✓ Valid Visa
Length: 16
Luhn: passes
Issuer: Visa (IIN 4xxxxx)Strips spaces, runs the Luhn algorithm, and reports the issuer from the IIN prefix.
Detect an American Express number
3782 822463 10005✓ Valid Amex
Length: 15
Luhn: passes
Issuer: American Express (IIN 37xxx)Recognizes the 34/37 IIN prefix and the 15-digit length band that distinguishes Amex from Visa and Mastercard.
About this tool
The Credit Card Validator checks whether a card number is structurally valid and identifies the issuing network. It strips spaces and dashes, runs the Luhn checksum, and matches the IIN/BIN prefix against the major networks — Visa, Mastercard, American Express, Discover, JCB, Diners Club, Maestro and UnionPay.
Validation is purely local: the number is never transmitted, so it is safe to inspect production card data or QA test cards without leaving a trace. Luhn-validity confirms the format, not that the account is real — only the payment processor can confirm that.
How to use
Paste a card number
Enter the number with or without spaces and dashes; both are accepted and stripped before validation.
Read the result
The tool reports whether the number passes the Luhn check, the detected network, and the expected length band for that network.
Use it to catch typos
Run a customer-entered number through the validator before submitting it, so a transposed digit fails immediately instead of triggering a decline at the gateway.
Use cases
Catching typos in payment forms
Validate a card number client-side before submitting, so a transposed digit fails immediately instead of triggering a declined transaction at the gateway.
Identifying the issuer on the back-end
Return the card network (Visa, Mastercard, Amex, …) from the BIN so your checkout can route to the right processor or apply network-specific rules.
QA for test cards
Sanity-check that test card numbers in your QA suite are still Luhn-valid after a copy-paste or schema change.
Common mistakes
Mistake:Believing a valid card number means the card is real.
Fix:Luhn and IIN confirm the format and the issuer, not that the account exists or has funds. Only the payment processor can confirm that.
Mistake:Logging the raw card number for debugging.
Fix:Luhn-valid numbers are still payment card data. Mask them (e.g. keep only the last four digits) and never log them in plaintext, even temporarily.
Mistake:Assuming a single regex covers every network.
Fix:Each issuer has its own IIN prefix and length band. Use a dedicated validator, not a regex, so 15-digit Amex and 16-digit Visa are both recognised correctly.
Frequently asked questions
References & standards
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