Web開発
Credit Card Validator
Luhnアルゴリズムでカード番号を検証し、決済ネットワークと桁数を判定します。すべてブラウザ内で計算され、番号はどこにも送信されません。
よくある質問
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.