HTTP

HTTP (Hypertext Transfer Protocol) is the application-layer protocol that powers the World Wide Web. Originally designed for retrieving hypertext documents (RFC 1945, HTTP/1.0 in 1996), it has evolved Into a general-purpose application protocol used for APIs, streaming, IoT communication, and Virtually every client-server interaction on the Internet.

This section covers HTTP/1.1 (RFC 9112), HTTP/2 (RFC 9113), HTTP/3 (RFC 9114), and the practical Aspects of deploying and debugging HTTP-based services.

HTTP/1.1 (originally RFC 2616, now obsoleted by RFC 9110-9114) is the foundational version of HTTP. Despite being over 25 years old, it remains the most widely deployed version and is still the Default for many client-server interactions.

HTTP defines methods that indicate the desired action on a resource:

Idempotent: Repeating the request produces the same result. PUT /users/1 with the same payload Creates or replaces user 1 — calling it multiple times has the same effect. POST /users creates a New user each time.

Safe: Does not modify server state. GET should never have side effects (though in practice, Many APIs violate this).

# HTTP methods with curl
curl -X GET https://api.example.com/users/1
curl -X POST -H "Content-Type: application/json" -d "{"name":"Alice"}' https://api.example.com/users
curl -X PUT -H "Content-Type: application/json" -d '{"name":"Alice Updated"}' https://api.example.com/users/1
curl -X DELETE https://api.example.com/users/1
curl -X PATCH -H "Content-Type: application/json" -d '{"name":"Bob"}' https://api.example.com/users/1
curl -X OPTIONS https://api.example.com/users
curl -X HEAD https://api.example.com/users/1

Status codes indicate the result of the request. They are grouped into five classes:

1xx — Informational:

2xx — Success:

3xx — Redirection: