IETF Internet Standards
The Internet Engineering Task Force (IETF) produces Internet Standards (STDs) and Best Current Practices (BCPs) covering core internet protocols including HTTP, TLS, OAuth, OpenID Connect, JSON, and many more. IETF RFCs form the normative basis for most web API standards. Key API-related RFCs include RFC 9110 (HTTP Semantics), RFC 6749 (OAuth 2.0), RFC 7519 (JWT), RFC 7946 (GeoJSON), and RFC 8259 (JSON).