CVV2 (also known as CVC2 or CID) is a three or four digit value that is uniquely derived for each credit card account.

On Visa and MasterCard cards, it is a three digit value printed in reverse italic characters on the signature panel following the last 4 digits of the account number.

On American Express cards, it is a four digit value printed on the front of the card, usually on the right side.

CVV2 is required for fraud protection.