What is HTTP (Hypertext Transfer Protocol)?

• HTTP is an application-layer protocol used for transmitting data over the web.
• It is the foundation of data communication for the World Wide Web.
• It is a reliable protocol that depends on TCP in the transport layer.
• It defines a set of rules for sending hypertext between two machines over a network.
• Uses a client-server model where the client sends requests, and the server sends responses.
• It will define how a machine will format, read and transmit hypertext from one machine to another.
• Throughout the years, HTTP has developed to become a more general purpose application layer protocol and is now capable of not just transmitting hypertext but mostly any kind of data images, text, json etc.

Hypertext is text displayed on a digital device that contains links (hyperlinks) to other text or resources. It allows users to navigate between different documents or parts of a document by clicking on the links. This makes information non-linear and interactive, unlike plain text. The web uses hypertext extensively in the form of HTML (Hypertext Markup Language) to create interconnected web pages.

How HTTP Works:

• The client (usually a web browser) initiates a request to the server.
• The server processes the request and sends back a response.
• Communication happens over TCP/IP.

Evolution of HTTP:

HTTP/1.0 (1996):

• Introduced HTTP headers, status codes, and content types.
• Supported POST and HEAD methods.
• No persistent connections — each request opened a new TCP connection.

HTTP/1.1 (1997):

• Persistent connections (Keep-Alive) to handle multiple requests over one TCP connection.
• Chunked transfer encoding for dynamic content.
• Cache control and better error handling.
• Pipelining (though not widely supported).

HTTP/2 (2015):

• Binary protocol instead of text for better performance.
• Multiplexing: Multiple requests in parallel over a single connection.
• Header compression using HPACK to reduce overhead.
• Stream prioritization for efficient resource loading.

HTTP/3 (Upcoming/Recent):

• Uses QUIC protocol over UDP for faster connection setup.
• Reduced latency with zero-round-trip time (0-RTT) for better performance.
• Built-in encryption with TLS 1.3.
• Resilient to packet loss compared to TCP.

HTTP Request Structure: