Which protocol does an API typically use for communication?

APIs, or Application Programming Interfaces, most commonly use HTTP (Hypertext Transfer Protocol) for communication over the web. This is due to several factors, including HTTP's compatibility with web technologies and its ability to handle requests and responses in a straightforward manner.

HTTP is well-suited for RESTful APIs, which are a popular architectural style for designing networked applications. It provides a clear framework for sending requests to a server and receiving a response, allowing applications to communicate using standard methods like GET, POST, PUT, and DELETE. This simplicity and ubiquity of HTTP make it a preferred choice for web-based APIs, allowing developers to create services that are accessible over the internet.

Other protocols, like SMTP (Simple Mail Transfer Protocol), are specialized for email communication and not designed for API interactions. TCP (Transmission Control Protocol) serves as a foundational transport layer protocol for many higher-level protocols but does not offer the direct application-level functionalities that HTTP provides. FTP (File Transfer Protocol) is primarily utilized for file transfers and lacks the structure required for API functions. Hence, HTTP stands out as the primary protocol utilized by APIs for web communication.