Internet

== Applications and services ==
The Internet carries many [[network service|applications and services]], most prominently the World Wide Web, including [[social media]], [[electronic mail]], [[mobile app]]lications, [[multiplayer online game]]s, [[Internet telephony]], [[file sharing]], and [[streaming media]] services.

Most [[Server (computing)|servers]] that provide these services are today hosted in [[data center]]s, and content is often accessed through high-performance [[content delivery network]]s.

=== World Wide Web ===
{{Main|World Wide Web}}
[[File:First Web Server.jpg|thumb|This [[NeXT Computer]] was used by [[Tim Berners-Lee]] at [[CERN]] and became the world's first [[Web server]].]]

The World Wide Web is a global collection of [[documents]], [[Computer graphics|images]], [[multimedia]], applications, and other resources, logically interrelated by [[hyperlink]]s and referenced with [[Uniform Resource Identifier]]s (URIs), which provide a global system of named references. URIs symbolically identify services, [[web servers]], databases, and the documents and resources that they can provide. [[Hypertext Transfer Protocol]] (HTTP) is the main access protocol of the World Wide Web. [[Web service]]s also use HTTP for communication between software systems for information transfer, sharing and exchanging business data and logistics and is one of many languages or protocols that can be used for communication on the Internet.<ref>{{cite web|url=http://www.webopedia.com/DidYouKnow/Internet/Web_vs_Internet.asp |title=The Difference Between the Internet and the World Wide Web |work=Webopedia |publisher=QuinStreet Inc. |date=24 June 2010 |access-date=1 May 2014 |url-status=live |archive-url=https://web.archive.org/web/20140502001005/http://www.webopedia.com/DidYouKnow/Internet/Web_vs_Internet.asp |archive-date=2 May 2014 }}</ref>

World Wide Web browser software, such as [[Microsoft]]'s [[Internet Explorer]]/[[Microsoft Edge|Edge]], [[Mozilla Firefox]], [[Opera (web browser)|Opera]], [[Apple Inc.|Apple]]'s [[Safari (web browser)|Safari]], and [[Google Chrome]], enable users to navigate from one web page to another via the hyperlinks embedded in the documents. These documents may also contain any combination of [[computer data]], including graphics, sounds, [[Plain text|text]], [[web video|video]], [[multimedia]] and interactive content that runs while the user is interacting with the page. [[Client-side scripting|Client-side software]] can include animations, [[web game|games]], [[office applications]] and scientific demonstrations. Through [[keyword (Internet search)|keyword]]-driven [[Internet research]] using [[Web search engine|search engines]] like [[Yahoo! Search|Yahoo!]], [[Bing (search engine)|Bing]] and [[Google Search|Google]], users worldwide have easy, instant access to a vast and diverse amount of online information. Compared to printed media, books, encyclopedias and traditional libraries, the World Wide Web has enabled the decentralization of information on a large scale.

The Web has enabled individuals and organizations to [[publish]] ideas and information to a potentially large [[audience]] online at greatly reduced expense and time delay. Publishing a web page, a blog, or building a website involves little initial [[cost]] and many cost-free services are available. However, publishing and maintaining large, professional web sites with attractive, diverse and up-to-date information is still a difficult and expensive proposition. Many individuals and some companies and groups use ''web logs'' or blogs, which are largely used as easily updatable online diaries. Some commercial organizations encourage [[employees|staff]] to communicate advice in their areas of specialization in the hope that visitors will be impressed by the expert knowledge and free information and be attracted to the corporation as a result.

[[Online advertising|Advertising]] on popular web pages can be lucrative, and [[e-commerce]], which is the sale of products and services directly via the Web, continues to grow. Online advertising is a form of [[marketing]] and advertising which uses the Internet to deliver [[promotion (marketing)|promotional]] marketing messages to consumers. It includes email marketing, [[search engine marketing]] (SEM), social media marketing, many types of [[display advertising]] (including [[web banner]] advertising), and [[mobile advertising]]. In 2011, Internet advertising revenues in the United States surpassed those of [[cable television]] and nearly exceeded those of [[broadcast television]].<ref name="IAB2012">{{cite web |url = http://www.iab.net/media/file/IAB_Internet_Advertising_Revenue_Report_FY_2012_rev.pdf |title = IAB Internet advertising revenue report: 2012 full year results |date = April 2013 |publisher = PricewaterhouseCoopers, Internet Advertising Bureau |access-date = 12 June 2013 |archive-url = https://web.archive.org/web/20141004001439/http://www.iab.net/media/file/IAB_Internet_Advertising_Revenue_Report_FY_2012_rev.pdf |archive-date = 4 October 2014 }}</ref>{{rp|19}} Many common online advertising practices are controversial and increasingly subject to regulation.

When the Web developed in the 1990s, a typical web page was stored in completed form on a web server, formatted in [[HTML]], ready for transmission to a web browser in response to a request. Over time, the process of creating and serving web pages has become dynamic, creating a flexible design, layout, and content. Websites are often created using [[content management]] software with, initially, very little content. Contributors to these systems, who may be paid staff, members of an organization or the public, fill underlying databases with content using editing pages designed for that purpose while casual visitors view and read this content in HTML form. There may or may not be editorial, approval and security systems built into the process of taking newly entered content and making it available to the target visitors.

=== Communication ===
[[Email]] is an important communications service available via the Internet. The concept of sending electronic text messages between parties, analogous to mailing letters or memos, predates the creation of the Internet.<ref>{{cite journal|first=Ron|last=Brown|title=Fax invades the mail market|url=https://books.google.com/books?id=Ry64sjvOmLkC&pg=PA218|journal=New Scientist|volume=56|issue=817|date=October 26, 1972|pages=218–221}}</ref><ref>{{cite journal|first=Herbert P.|last=Luckett|title=What's News: Electronic-mail delivery gets started|url=https://books.google.com/books?id=cKSqa8u3EIoC&pg=PA85|journal=Popular Science|volume=202|issue=3|date=March 1973|page=85}}</ref> Pictures, documents, and other files are sent as [[email attachment]]s. Email messages can be [[Carbon copy|cc-ed]] to multiple [[email address]]es.

[[Internet telephony]] is a common communications service realized with the Internet. The name of the principal internetworking protocol, the Internet Protocol, lends its name to [[voice over Internet Protocol]] (VoIP). The idea began in the early 1990s with [[walkie-talkie]]-like voice applications for personal computers. VoIP systems now dominate many markets and are as easy to use and as convenient as a traditional telephone. The benefit has been substantial cost savings over traditional telephone calls, especially over long distances. [[Cable modem|Cable]], [[ADSL]], and [[mobile data]] networks provide [[Internet access]] in customer premises<ref name=EBSCOhost>{{cite journal|last=Booth|first=C|title=Chapter 2: IP Phones, Software VoIP, and Integrated and Mobile VoIP|journal=Library Technology Reports|year=2010|volume=46|issue=5|pages=11–19}}</ref> and inexpensive VoIP network adapters provide the connection for traditional analog telephone sets. The voice quality of VoIP often exceeds that of traditional calls. Remaining problems for VoIP include the situation that emergency services may not be universally available and that devices rely on a local power supply, while older traditional phones are powered from the local loop, and typically operate during a power failure.

=== Data transfer ===
[[File sharing]] is an example of transferring large amounts of data across the Internet. A [[computer file]] can be emailed to customers, colleagues and friends as an attachment. It can be uploaded to a website or [[File Transfer Protocol]] (FTP) server for easy download by others. It can be put into a "shared location" or onto a [[file server]] for instant use by colleagues. The load of bulk downloads to many users can be eased by the use of "[[Web mirror|mirror]]" servers or [[peer-to-peer]] networks. In any of these cases, access to the file may be controlled by user [[authentication]], the transit of the file over the Internet may be obscured by [[encryption]], and money may change hands for access to the file. The price can be paid by the remote charging of funds from, for example, a credit card whose details are also passed—usually fully encrypted—across the Internet. The origin and authenticity of the file received may be checked by [[digital signature]]s or by [[MD5]] or other message digests. These simple features of the Internet, over a worldwide basis, are changing the production, sale, and distribution of anything that can be reduced to a computer file for transmission. This includes all manner of print publications, software products, news, music, film, video, photography, graphics and the other arts. This in turn has caused seismic shifts in each of the existing industries that previously controlled the production and distribution of these products.

[[Streaming media]] is the real-time delivery of digital media for immediate consumption or enjoyment by end users. Many radio and television broadcasters provide Internet feeds of their live audio and video productions. They may also allow time-shift viewing or listening such as Preview, Classic Clips and Listen Again features. These providers have been joined by a range of pure Internet "broadcasters" who never had on-air licenses. This means that an Internet-connected device, such as a computer or something more specific, can be used to access online media in much the same way as was previously possible only with a television or radio receiver. The range of available types of content is much wider, from specialized technical [[webcast]]s to on-demand popular multimedia services. [[Podcast]]ing is a variation on this theme, where—usually audio—material is downloaded and played back on a computer or shifted to a [[portable media player]] to be listened to on the move. These techniques using simple equipment allow anybody, with little censorship or licensing control, to broadcast audio-visual material worldwide.

Digital media streaming increases the demand for network bandwidth. For example, standard image quality needs 1 Mbit/s link speed for SD 480p, HD 720p quality requires 2.5 Mbit/s, and the top-of-the-line HDX quality needs 4.5 Mbit/s for 1080p.<ref>{{cite web |last=Morrison |first=Geoff |url=http://www.nbcnews.com/id/40241749 |title=What to know before buying a 'connected' TV – Technology & science – Tech and gadgets – Tech Holiday Guide |publisher=NBC News |date=18 November 2010 |access-date=8 August 2011 |archive-url=https://web.archive.org/web/20200212091603/http://www.nbcnews.com/id/40241749 |archive-date=12 February 2020 |url-status=live }}</ref>

[[Webcam]]s are a low-cost extension of this phenomenon. While some webcams can give full-frame-rate video, the picture either is usually small or updates slowly. Internet users can watch animals around an African waterhole, ships in the [[Panama Canal]], traffic at a local roundabout or monitor their own premises, live and in real time. Video [[chat rooms]] and [[video conferencing]] are also popular with many uses being found for personal webcams, with and without two-way sound. YouTube was founded on 15 February 2005 and is now the leading website for free streaming video with more than two billion users.<ref>{{Cite web|title=Press|url=https://www.youtube.com/about/press/|access-date=19 August 2020|website=YouTube|archive-date=11 November 2017|archive-url=https://web.archive.org/web/20171111094352/https://www.youtube.com/yt/about/press/|url-status=live}}</ref> It uses an HTML5 based web player by default to stream and show video files.<ref>{{Cite news|url=https://youtube-eng.googleblog.com/2015/01/youtube-now-defaults-to-html5_27.html|title=YouTube now defaults to HTML5|work=YouTube Engineering and Developers Blog|access-date=10 September 2018|language=en-US|archive-url=https://web.archive.org/web/20180910204225/https://youtube-eng.googleblog.com/2015/01/youtube-now-defaults-to-html5_27.html|archive-date=10 September 2018|url-status=live}}</ref> Registered users may upload an unlimited amount of video and build their own personal profile. [[YouTube]] claims that its users watch hundreds of millions, and upload hundreds of thousands of videos daily.