What is HTTP?

Hypertext Transfer Protocol (HTTP) is the foundational communication protocol used on the World Wide Web. It defines how messages are formatted and transmitted between clients, typically web browsers, and servers hosting web content. HTTP is an application-layer protocol built on top of the Transmission Control Protocol (TCP) or, in the case of HTTP/3, the QUIC transport protocol over UDP. Its primary purpose is to make web resources like HTML pages, images, scripts, APIs, and other content accessible and deliverable across networks.

Evolution of HTTP

HTTP has evolved through several versions:

• HTTP/0.9 (1991): A simple protocol supporting only raw data transfer through GET requests.
• HTTP/1.0 (1996): Introduced headers, status codes, and additional methods beyond GET.
• HTTP/1.1 (1997): Improved performance with persistent connections, chunked transfers, and caching mechanisms.
• HTTP/2 (2015): Enhanced efficiency through multiplexing, header compression, and server push capabilities.
• HTTP/3 (2022): Built on QUIC (a transport protocol running over UDP), offering faster connection establishment and improved reliability over modern networks.

Core Model: Request and Response

HTTP follows a request-response model. A client sends an HTTP request to a server, which processes the request and returns an HTTP response. The request specifies a method, such as GET to retrieve data or POST to submit data, and includes headers that convey metadata. The response includes a status code indicating the outcome, e.g., 200 OK for success, 404 Not Found for missing resources, along with the requested content or additional information.

Stateless Nature

A defining characteristic of HTTP is that it is stateless. Each request is treated as independent, with no inherent memory of previous interactions. This design simplifies server implementation but also introduces challenges for maintaining user sessions. To address this, mechanisms such as cookies, sessions, and tokens are used to preserve state across multiple requests.

note

• Cookies: Small pieces of data stored on the client and sent with requests. They can hold session identifiers or user preferences.
• Sessions: Server-side tracking linked to a session identifier stored in a cookie. Sessions allow servers to maintain user state across multiple requests.
• Tokens: Like JSON Web Tokens (JWTs) used in Application Programming Interfaces (APIs) to validate authenticated users. Tokens are often included in request headers to authorize access to protected resources.

Importance in Modern Systems

HTTP underpins nearly all web interactions. It defines how browsers load pages, how APIs communicate, and how distributed systems exchange data. Its simplicity, extensibility, and widespread adoption have allowed it to remain relevant despite decades of evolution and make it one of the most critical protocols in modern networking.

Summary

HTTP is the protocol that powers the web. Its design makes it a flexible and widely adopted standard. Through improvements across versions, it continues to provide the backbone for efficient communication across the Internet.