(HTTP|HTTPS) - Hypertext Transfer Protocol

About

Hypertext Transfer Protocol (HTTP) is the transfer protocol to exchange or transfer web resource between nodes (host).

The H in HTTP means an hypertext (ie HTML).

The protocol was first designed to transport hypertext (ie HTML) but it has been extended to be able to fetch any type of resources.

HTTP was originally designed to be usable as an interface to distributed object systems.

This is the most common protocol for transferring web resource (content) from server to client (user agent).

HTTP is a request/response standard of a client and a server.

A client is the end-user known as user-agent, the server is the web site.

In between the user agent (browser mostly) and the origin server, intermediaries may be used in the transport chain (routing). They are known as proxies ie:

Resources to be accessed by HTTP are identified using Uniform Resource Identifiers (URIs)—or, more specifically, Uniform Resource Locators (URLs)—using the http: or https URI schemes.

HTTP allows an open-ended set of methods and headers that indicate the purpose of a request. HTTP is also used as a generic protocol for communication between user agents and proxies/gateways to other Internet systems.

HTTP provides also data transfer.

RFC

HTTP is defined in rfc2616 - Hypertext Transfer Protocol – HTTP/1.1.

It is the union of a set of RFCs:

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