ISO 8583: THE LANGUAGE OF CREDIT CARDS

Summary from the TLDR Web Dev newsletter

ISO 8583 is a standard for real-time payment messages between banks and merchants, used in most card transactions. The standard has evolved over time, leading to variations across networks due to flexibility in field encoding and the addition of network-specific fields. This has made it complex, due to optional fields, diverse encoding schemes, and different ways of handling nested messages.