ACI Worldwide makes software that processes and manages digital payments for banks, merchants, and billers. Its software handles the authentication, authorization, routing, settlement, fraud detection, and reconciliation that sit beneath any digital payment transaction. ACI's largest customer base is banks — nearly all of the world's top 10 banks by assets use ACI software — which use ACI's issuing and acquiring solutions to process card transactions and connect to real-time payment rails. ACI also serves over 80,000 merchants globally through its Payments Orchestration Platform, and provides electronic bill payment services to utilities, insurers, healthcare companies, and government entities through its Speedpay business. ACI organizes its business into two segments: Payment Software (~61% of revenue), which covers banks and merchants and generates most of its revenue outside the U.S., and Biller (~39% of revenue), which is U.S.-only and has a more stable, recurring revenue profile. ACI licenses its software on-premises under multi-year term contracts, as a SaaS/PaaS offering, or on a consumption basis tied to transaction volumes. Because ACI's software is mission-critical infrastructure that is complex and expensive to replace, customer switching costs are high and revenue is durable. ACI's most important growth initiative is Connetic, a cloud-native payments hub platform launched in 2025 aimed at expanding ACI's addressable market beyond large banks to include mid-sized banks, fintechs, and non-bank financial institutions.