What is the primary function of API Client Whitelisting in Salesforce?

API Client Whitelisting in Salesforce serves as a security measure designed to enhance the control an organization has over which client applications are permitted to make API calls. By requiring explicit approval for each client app, it effectively restricts access to the Salesforce data and services until an administrator has defined the allowed applications. This approach mitigates potential security risks that could arise from unauthorized access, ensuring that only trusted applications can interact with Salesforce APIs.

The other options do not align with the principle of security through restrictions. Allowing all client apps access by default (the first choice) would undermine the security model by creating vulnerabilities. Providing unlimited API access to all apps (the third choice) contradicts the fundamental intent of whitelisting as it would negate any control over accessing sensitive data. Lastly, enhancing the speed of API calls (the fourth choice) is not a primary function of whitelisting; rather, it focuses on managing which applications can access the API rather than impacting performance.