A validation code—also known as a CVV, CV2, or CVV2 code—is a series of three or four numbers located on the front or back of a credit card. It is intended to provide an additional layer of security for credit card transactions that take place online or over the phone.

Most credit card issuers place their validation codes on the back of the card, on the far-right side of the signature panel. On American Express (AXP) cards, however, the validation code is printed on the front of the card.