Methods and systems are disclosed for the generation and use of merchant-customizable token formats that define tokens that represent credit card and other payment numbers in online transactions. The tokens, which are used instead of the card numbers themselves for security, can be specified by the token format to have a certain number of characters, have certain fields reserved for major card identifiers, use encryption and/or randomization, be alphanumeric, and have other formatting. The customized tokens can be used with legacy equipment that uses longer or shorter card numbers than the standard sixteen-digit payment card number format and can be less likely to be recognized as related to card numbers by identify thieves.