Web Development
Credit Card Validator
Validate a card number with the Luhn algorithm, detect the payment network and length. Everything runs in the browser — the number is never sent anywhere.
The Luhn algorithm is a checksum most payment networks append to a card number to catch accidental typing errors (one transposed or mistyped digit). This tool checks a number against Luhn and identifies the payment network from its prefix (BIN).
How to use it
- Enter a card number — the Luhn check and network detection happen instantly as you type.
- Spaces and hyphens in the number are ignored automatically, so you don't need to strip them yourself.
- The tool shows the expected length for the detected network, so you can immediately see if digits are missing.
Common uses
- Validating a payment form on the frontend before submission — a basic sanity check before hitting the payment gateway.
- Generating test card numbers for development and QA (with a correct checksum, but not tied to real accounts).
- Quickly checking whether a manually entered number is just a typo-riddled string of random digits.
Things to keep in mind
A card passing the Luhn check doesn't mean it's active, unblocked, or even real — the check only catches obvious typing mistakes.
Card data is processed entirely in your browser and never sent anywhere, but for actual payments, always use a certified payment form (PCI DSS) rather than pasting a real card number into a third-party tool.
Article about this tool: The Luhn algorithm: how a card number gets checked for correctness
Frequently asked questions
Does a passing check mean the card is real and has funds?
No — this tool only verifies the Luhn checksum and the expected digit length for the detected network; it can't tell you whether the card actually exists, is active, or has funds, since that requires contacting the card issuer.
How does the Luhn algorithm work?
It doubles every second digit from the right, sums the digits of the results together with the untouched digits, and checks that the total is a multiple of 10 — it catches most typos and transposed digits but isn't a fraud check.
Is my card number sent anywhere?
No, validation happens entirely in your browser and the number is never transmitted or stored.
How is the payment network (Visa, Mastercard, etc.) detected from a card number?
From the first few digits of the number, called the BIN (Bank Identification Number) — for example Visa numbers always start with 4, and Mastercard with the 51–55 or 2221–2720 ranges; payment forms use that prefix to show the network's icon before you even finish typing the number.
Can the BIN tell you which bank issued a card?
Partially — the first 6 digits (the extended BIN) usually identify not just the payment network but the specific issuing bank and card type (debit or credit), though pinpointing the exact bank requires specialized BIN lookup databases, not the Luhn algorithm itself.