Which method is used to connect systems and unify customer data?

API Integration is a method that allows different software systems to communicate with each other and share data seamlessly. By using APIs (Application Programming Interfaces), various applications can interact in real-time, ensuring that customer data is unified across different platforms. This is particularly vital for businesses that rely on multiple software tools to manage customer information, such as CRM systems, databases, and marketing platforms.

While API Integration is focused on establishing a connection for direct and real-time data exchange, it stands out from other methods. For instance, data migration pertains to transferring data from one system to another, which may not involve ongoing synchronization or unification of customer data once the transfer is complete. Data integration, in a broader sense, encompasses various techniques, including API integration, but it does not specifically highlight the use of APIs as the connective tissue for systems.

Data cleaning, on the other hand, focuses on ensuring that the data itself is accurate and consistent, rather than on connecting systems or unifying their data. Therefore, API Integration is the most appropriate method among the options given for connecting systems and achieving unified customer data through real-time interactions and data sharing.