Visa cards are identifiable by their account numbers, because they always begin with the digit 4, according to Cybersource, as of 2015. In addition, valid Visa credit cards are identifiable by the length of the account number, the brand mark and the hologram, explains UniBul Merchant Services.
Visa credit cards are marked on the front with the Visa brand logo and a dove-shaped hologram, reports UniBul. This hologram should appear to move as the card is rotated. Visa cards also have an account number that is always either 13 or 16 digits long. The first four digits are the card's BIN, or bank identification number, and they identify the card as a Visa. The first digit of a Visa BIN is always 4.