Hypertext Transfer Protocol (HTTP)
The application layer protocol that powers the World Wide Web and the majority of REST and HTTP APIs. HTTP/1.1 is defined in RFC 9110-9114, HTTP/2 in RFC 9113, and HTTP/3 in RFC 9114, the latter running over QUIC. HTTP defines methods, status codes, headers, content negotiation, caching, and conditional requests that underpin modern web APIs.
Other Resources
Specification
https://www.rfc-editor.org/rfc/rfc9110
Specification
https://www.rfc-editor.org/rfc/rfc9112
Specification
https://www.rfc-editor.org/rfc/rfc9113
Specification
https://www.rfc-editor.org/rfc/rfc9114
Working Group
https://datatracker.ietf.org/wg/httpbis/about/
APIsJSON
https://raw.githubusercontent.com/api-evangelist/communication-protocols/refs/heads/main/apis.yml