Credit Card Validator

A credit card validator checks whether a card number is well-formed — the right length, a recognized card-type pattern, and a passing Luhn checksum. It does NOT check whether a card is real, active, or has funds (that requires the payment network); it validates the number's STRUCTURE, catching typos and malformed numbers.

This is what payment forms do as their first check: before sending a card to the processor, they verify it at least looks like a valid card number — right length, valid checksum — to catch mistakes instantly rather than after a failed transaction.

Enter a card number and see whether it's structurally valid — format, detected card type, and Luhn check result.

What it checks and why: Luhn checksum — the algorithm (every valid card number satisfies it) that catches the vast majority of single-digit typos and transpositions; if a number fails Luhn, it's definitely mistyped or fake; card type detection — the number's prefix identifies the network (Visa starts with 4, Mastercard 51-55/2221-2720, Amex 34/37), useful for showing the right card logo and applying network-specific rules; and length — different networks use different lengths (Visa/MC 16, Amex 15).

Where it's used: testing payment validation — verifying your form's validation logic works (does it correctly pass valid numbers and reject invalid ones?); understanding card structure — learning how card numbers encode network and pass checksums; and catching input errors — the same first-line check real forms use. Important: passing validation means the number is well-FORMED, not that it's a real usable card — only the payment network knows if a card exists and can be charged. This is structure validation, the same as what a checkout form does before submission. Pair with our Credit Card Generator (which creates Luhn-valid test numbers to validate here) — together they let you test both sides of card-format handling in development.