How can an API perform authentication?

An API can perform authentication using tokens, API keys, or OAuth mechanisms because these methods provide secure ways to verify the identity of a user or application making the request. Tokens often carry encoded information that confirms the user’s identity, while API keys are unique identifiers assigned to clients to allow access to the API. OAuth is a widely used authorization framework that enables third-party applications to obtain limited access to user accounts without exposing credentials.

These approaches are designed to enhance security and streamline the authentication process, making it possible for APIs to manage access effectively while keeping user data safe. Moreover, they allow APIs to handle various scenarios, such as user interaction and automated processes, ensuring versatility in how authentication is implemented.

In contrast, the other options present limitations. For instance, using client IP addresses lacks reliability as an authentication method since IP addresses can change and may not uniquely identify users. Relying solely on username and password is less secure, especially if credentials can be intercepted or compromised. Lastly, tracking user session cookies, while useful for managing user sessions post-authentication, does not offer a comprehensive authentication mechanism on its own.