What is CCV?

CCV, is the security code printed on your credit card - a 3- or 4-digit number. This number is only printed on your card, and is not stored anywhere. The only way to know the number is to physically have the card, making this a valuable security measure.

MasterCard, Visa or Discover
ccv
Look on the back of your card, in the signature panel. The last three numbers are your security code.

American Express:

ccv

Look on the front of your card, above the embossed numbers. The four printed numbers are your security code.