Visa and Mastercard Explained: The Networks That Route Every Card Swipe

Despite being the most visible brands in payments, Visa and Mastercard don’t issue cards, hold your money, print plastic, or run the point-of-sale terminals — all of that belongs to issuing banks, payment processors, and merchant acquirers like Stripe, Square, and Adyen. What the card networks actually do is sit in the middle of a two-sided market, connecting cardholders and their issuers to merchants and acquirers. Their role reduces to four jobs: running a telecom network to route transaction messages, coordinating banks to settle money, setting fee-based incentives to grow participation, and writing and enforcing the rules (including dispute handling).

Technically, a network like Visa operates like a global switch. It runs hardened, disaster-resistant data centers and leased fiber to forward authorization requests from merchants to issuers, which approve or decline in real time. Card numbers function much like IP addresses — the first 6-8 digits (the BIN) identify the issuer. Authorization places a hold; later clearing submits the final amount; and settlement moves the actual funds, which Visa nets daily across participants. Its cross-border reach is a major value-add, acting as an adapter between banking systems and handling currency conversion so members don’t each need their own global relationships. That scale carries real balance-sheet risk: Visa reported holding $11.2 billion in liquidity for settlement backstops, with average daily settlement exposure of $84.3 billion and a fiscal-2024 peak of $137.4 billion.

The economics are counterintuitive. On a typical $100 US credit purchase with a 2.5% merchant discount rate, the issuing bank keeps roughly $2.00 (interchange), the processor about $0.35, and the network only about $0.15 (the assessment fee). The issuer earns the most because it absorbs the most risk — credit exposure plus zero-liability protection for lost or stolen cards. Crucially, the networks set the interchange and assessment fees, and interchange varies widely by card type, spend category, and transaction metadata, making the networks the quiet rule-setters behind the entire system.