Hypertext Transfer Protocol

URL beginning with the HTTP scheme and the WWW domain name label
Tim Berners-Lee
An HTTP/1.1 request made using telnet. The request message, response header section, and response body are highlighted.

Application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems.

- Hypertext Transfer Protocol

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World Wide Web

World's dominant software platform.

The historic World Wide Web logo, designed by Robert Cailliau.
A web page displayed in a web browser
A global map of the Web Index for countries in 2014
This NeXT Computer was used by Sir Tim Berners-Lee at CERN and became the world's first Web server.
The World Wide Web functions as an application layer protocol that is run "on top of" (figuratively) the Internet, helping to make it more functional. The advent of the Mosaic web browser helped to make the web much more usable, to include the display of images and moving images (GIFs).
Graphic representation of a minute fraction of the WWW, demonstrating hyperlinks
A screenshot of a web page on Wikimedia Commons
Dynamic web page: example of server-side scripting (PHP and MySQL)
The usap.gov website
The inside and front of a Dell PowerEdge web server, a computer designed for rack mounting
Multiple web servers may be used for a high traffic website; here, Dell servers are installed together to be used for the Wikimedia Foundation.
The results of a search for the term "lunar eclipse" in a web-based image search engine

The information in the Web is transferred via the Hypertext Transfer Protocol (HTTP) to be accessed by users through software applications.

Web server

PC clients communicating via network with a web server serving static content only.
The inside and front of a Dell PowerEdge server, a computer designed to be mounted in a rack mount environment. It is often used as a web server.
Multiple web servers may be used for a high traffic website.
Web server farm with thousands of web servers used for super-high traffic websites.
ADSL modem running an embedded web server serving dynamic web pages used for modem configuration.
First web proposal (1989) evaluated as "vague but exciting..."
The world's first web server, a NeXT Computer workstation with Ethernet, 1990. The case label reads: "This machine is a server. DO NOT POWER IT DOWN!!"
Sun's Cobalt Qube 3 – a computer server appliance (2002, discontinued)
PC clients connected to a web server via Internet
PC clients communicating via network with a web server serving static and dynamic content.
Directory listing dynamically generated by a web server.
Chart:
Market share of all sites for most popular web servers 2005–2021
Chart:
Market share of all sites for most popular web servers 1995–2005

A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS.

Transport Layer Security

Cryptographic protocol designed to provide communications security over a computer network.

Example of a website with digital certificate
Simplified illustration of the full TLS 1.2 handshake with timing information.

For example, port 80 is typically used for unencrypted HTTP traffic while port 443 is the common port used for encrypted HTTPS traffic.

Web browser

Application software for accessing the World Wide Web or a local website.

Traditional browser arrangement: UI features above page content
Nicola Pellow and Tim Berners-Lee in 1992
Marc Andreessen, lead developer of Mosaic and Navigator, in 2007

In Hypertext Transfer Protocol technical texts, web browsers (and other clients) are commonly referred as user agents.

Website

Collection of web pages and related content that is identified by a common domain name and published on at least one web server.

The usap.gov website
The nasa.gov home page in 2015
Server-side programming language usage in 2016.

Before the introduction of the Hypertext Transfer Protocol (HTTP), other protocols such as File Transfer Protocol and the gopher protocol were used to retrieve individual files from a server.

URL

Reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it.

The historic World Wide Web logo, designed by Robert Cailliau.

URLs occur most commonly to reference web pages (http) but are also used for file transfer (ftp), email (mailto), database access (JDBC), and many other applications.

HTTP/2

HTTP/2 (originally named HTTP/2.0) is a major revision of the HTTP network protocol used by the World Wide Web.

Web crawler

About the internet bot.

High-level architecture of a standard Web crawler
Evolution of Freshness and Age in a web crawler

Endless combinations of HTTP GET (URL-based) parameters exist, of which only a small selection will actually return unique content.

User agent

Any software, acting on behalf of a user, which "retrieves, renders and facilitates end-user interaction with Web content".

Computer simulation, one of the main cross-computing methodologies.

In HTTP, SIP, and NNTP protocols, this identification is transmitted in a header field User-Agent.

Web cache

System for optimizing the World Wide Web.

The historic World Wide Web logo, designed by Robert Cailliau.

A proxy server sitting between the client and web server can evaluate HTTP headers and choose whether to store web content.