Mastercard and Visa are the dominant global payment networks. Mastercard and Visa simply provide the rules, technology and communications network that allow thousands of financial institutions to work together. Amex combines the roles of card issuer, payments network and merchant acquirer within a single business. Use the same card abroad and the payment is likely to travel across the Mastercard or Visa network instead. In effect, the duopoly are moving from simply operating payment networks to providing the software that helps many different payment networks function, and keeping payments safe and reliable.