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What is a Web Browser

bullet Introduction

A browser is a web application that is used to retrieve and display information available on the 'web' (World Wide Web). The web is an information system found on the Internet, and is based upon a client-server model: where a client application (browser) requests and retrieves documents from web servers connected to the Internet. Browsers use a type of URI, named a Uniform Resource Locators (URL), to locate web resources, and HTTP (HyperText Transfer Protocol) to retrieve the resource. Alongside locating and retrieving web information, browsers also render and display the information and can potentially interact with it.

The first web browser, displayed on a monitor at CERN
(Pictured: The earliest web browser displayed on a CERN computer, operated by Tim Berners-Lee)

The way in which users interact with browsers has largely remained the same since the creation of early browsers: 1) Direct input of a URL into the address bar of a browser; 2) By clicking on a hyperlink - also referred to as 'link'; 3) Bookmark/Favourite: a list of saved URLs. When a link is clicked, or a URL is directly inputted into an address bar, browsers use a request-response protocol, named the Hypertext Transfer Protocol (HTTP), to send a HTTP request to the server that hosts the resource, and if authorised, will then retrieve and render it. HTTP will use additional protocols like the TCP (Transmission Control Protocol) to reliable retrieve the resource.

When the web was launched in the early 1990s, the vast majority of information uploaded to it was in the form HTML documents, therefore, the main functionality of browsers was and still is rendering HTML and CSS. The standard specification for how browsers should render HTML is provided by the W3C (World Wide Web Consortium). Modern browsers usually consist of the following components: user interface, networking, data storage, querying engine, JavaScript interpreter, and rendering engine. Some example of web browser rendering / layout engines are: Gecko (Mozilla Firefox), WebKit (Apple Safari), Trident (Internet Explorer), Presto (Opera), Blink (Chrome), Tasman and KHTML.

While browsers attempt to be compatible with the majority of web content, they are not exclusively cross platform. The earliest web browsers were primarily compatible with Unix. Modern day browsers, like Chrome, have versions available for the following platforms: Android, iOS, Windows (10/8.1/8/7 32-bit), Mac OS X (10.9 or later) and Linux. The earliest browsers were exclusively designed for use on desktop computers, due to the exponential use of smartphones and tablets to access the Internet, most modern browsers have a mobile version. While browsers are usually designed and targeted for a specific platform, they are typically written in the C++ programming language: Chrome: written in C/C++, Python; Firefox: written in C/C++; Internet Explorer: written in C++; Opera:written in C++; and Safari: written in C++ and Objective-C.

Some early browsers were not free: Netscape Navigator had close to 90% of the browser market in 1994-1995 and was able to charge $49 for its browser. However, in 1996, Microsoft released their Internet Explorer browser for free, and since then, the vast majority of browsers are free for download.

bullet History

In 1990, the first browser was developed by Tim Berners-Lee while he worked at CERN (a European center for physics research) inventing the World Wide Web, and was publicly released in 1991. The World Wide Web was launched on the 6th of August 1991, and the name of Berners-Lee's browser was 'WorldWideWeb'. The WorldWideWeb was a basic text-only browser, and was quickly improved upon in terms of functionality and platform compatibility.

Worldwideweb browser
(Pictured: WideWideWeb browser's GUI)

Provided below, is a list of early web browsers that were developed from 1991-1992.

  1. MacWWW: the first browser developed for the Apple Macintosh platform.
  2. Line Mode Browser: expanded the compatibility of the WorldWideWeb browser.
  3. Lynx: Developed by team of students at the University of Kansas.
  4. ViolaWWW: Developed by Pei-Yuan Wei, released on March 9, 1992.
  5. MidasWWW: Developed at the (SLAC) Stanford Linear Accelerator Center.
  6. Cello: The first browser developed for the Microsoft Windows operating system.
  7. Erwise: Developed by students of the Helsinki University of Technology.

The first browser to achieve widespread popularity was NCSA Mosaic. Mosaic was designed by a team of software engineers at the National Center for Supercomputing Applications (NCSA) that included Marc Andreessen and Eric Bina. The Mosaic browser is acclaimed for popularising the web, and invented many of the principle features found in modern browsers - the image, shown below, is the GUI of Mosaic:

GUI of Mosaic, one of the first web browsers and one of the most important
(Pictured: Mosaic menu bar, similar designs were used in more modern web browsers)

The characteristics of the Mosaic GUI - with its URL address bar, history manager, tools - is still retained by most modern browsers. It is generally accepted that Netscape Navigator and Internet Explorer copied the layout and features of Mosaic; that is to be expected with Netscape Navigator, as it was developed by the same team of developers that created Mosaic - Marc Andreessen etc. Mosaic's legacy has continued to the present day: in 1998 the Mozilla community was created by members of Netscape. Mozilla is a combination of the words: Mosaic and Godzilla. Mozilla is a community/corporation/foundation that manages the development of the open source release of Netscape Communicator (successor to Netscape Navigator). Mozilla released Firefox in 2002: Firefox continues the legacy of Netscape Navigator, and in some senses the Mosaic browser.

Mosaic was originally designed to run on the Unix platform, and only at a later date was it released for the Apple Macintosh and the Microsoft Windows platform. Why was Mosaic originally released on Unix? In the early 1990s the Internet was only just beginning to be commercially deregulated and most households (in developed nations) did not have access to the Internet. Unix was 'Internet ready', whereas most home operating systems, like Windows, did not focus on network access; the first edition of Windows 95 did not come with a TCP/IP installation. However, by the mid 1990s, interest in the Internet had expanded, and many commercial Internet Service Providers began offering access to home users. When later editions of Windows 95 began packaging the Internet Explorer browser with the operating system, and installing TCP/IP as standard, the majority of Internet users had switched from being Unix users to Windows users. This trend has continued to the present day (2014), and has resulted in software developers primarily designing browsers for the Windows platform.

The success of the Mosaic browser led to the creation of the Mosaic Communications Corporation on the 4th of April 1994; this newly formed corporation retained the majority of software engineers who designed the original Mosaic browser. The first browser released by the Mosaic Communications Corporation was Mosaic Netscape 0.9. Eventually, the Mosaic Communications Corporation was renamed to the Netscape Communications Corporation, and the browser renamed to the Netscape Navigator. By 1995, Netscape Navigator was the most popular browser, but it was not to last, Netscape would soon be embroiled in a fierce battle with Microsoft; who had begun packaging their Internet Explorer browser with Windows 95. Netscape accused Microsoft of an illegal monopolistic action by "giving away" (packaging) Internet Explorer with the Windows operating system. The whole 'furor' eventually resulted in a lawsuit (United States v. Microsoft Corporation, for committing monopolization - 253 F.3d 34), but, it did not stop Internet Explorer from becoming the preeminent web browser.

From 1997-2010, Internet Explorer was the most popular web browser used on the Internet; largely due to the fact that the majority of Internet users were Windows users. Apple released the Safari browser in 2003, and this browser, likewise, was the most popular browser used by Macintosh users. While browsers were released for other platforms - Unix, Linux, Amiga - they were niche browsers in terms of overall usage share (combined under 2% of overall browser usage). From 1997-2010, the vast majority of Internet users connected using a Windows or Apple computer, and the browsers used by these users tended to be the browser packaged with the systems operating system.

Since 2010, Internet Explorer began to face stiff competition from a selection of three new browsers: Opera, Chrome, and Firefox. Internet Explorer had often been the recipient of criticism due to security issues and it's 'bloated' code; this enabled Google (Chrome) to leverage its influence as the web most popular search engine, and open source projects like Mozilla (Firefox) (Netscape offspring) had retained a sizable usage share. In 2014, a 'rough' estimate of overall browser usage (provided by web counter providers) was: Chrome: 30%, Internet Explorer: 22%, Firefox: 19%, Safari: 15%, Opera: 6%, Android: 5% and Others: 3%. It is interesting to note that Android (a browser developed for mobile devices) had begun to take a small but sizable browser usage share. From 2010 on wards, technology experts predicted that mobile devices - and therefore mobile browsers - would increase exponentially in their use. Safari, for example, is also a mobile browser, alongside being a traditional browser, and accounts for upwards of 60% of all mobile browser usage.

In 2017, web counter companies (Statcounter, NetMarketShare, W3Counter) have released browser usage stats; web counters record web site visits and record the browser used for each visit. The stats released in 2017, by these three companies, differs slightly, but when combined roughly show the following usage stats: Chrome 65%, Firefox 13%, Internet Explorer 9%, Safari 5%, Edge 4% and Others 4%.

It should be noted however, that the impact a web browser has is not always related to the number of times it has been downloaded: The Tor browser is an example of a browser, that in no way equals the market usage of the aforementioned web browsers, but has massively impacted Internet security and anonymity. The Tor browser is a modified version of the Mozilla Firefox ESR that uses an 'anonymity network' to encrypt data and route it through a layer of 3 nodes. Based upon the principle of 'onion routing' -- which was developed by P.Syverson, M.Reed and D.Goldschlag in the 1990s to protect US intelligence communications -- the Tor Project was founded in the early 2000s by 7 individuals that included computer scientist Roger Dingledine. While the Tor browser has been criticised for enabling a 'dark web' -- that intelligence and law enforcement agencies have difficulty in penetrating -- Roger Dingledine has allegedly stated that the vast majority of Tor users use it to anonymously browse websites such as Facebook and Reddit. While Tor undoubtedly helps to protect privacy, Edward Snowden has allegedly claimed that some Tor nodes are operated by intelligence agencies, which may comprise the Tor network to a small extent.

bullet User Interface, Features and Compatibility

The user interface of most browsers tends to include the following elements:

1. Address bar (command line and prompt).

example of an address bar in a web browser

2. Back, forward, stop, refresh, and home buttons.

buttons to move inbetween viewed  web documents

3. Bookmarks (favourites in Internet Explorer) and history.

a list of favourites stored  in a list

The user interface of browsers is mostly used to locate web resources, and the above three elements enable: new resources to be inputted (address bar); recent resources accessed (back, refresh); and historical resources accessed (history and bookmarks). Modern browsers tend to go with a minimalist approach, like Chrome, to not confuse users with a plethora of buttons and menu options; which was not the case with some older browsers (Mosaic) that overloaded its GUI with buttons.

Features tend to be accessed deeper within the menu system of the browser; modern day browsers, as you would expect, contain far more features than their ancestors. There is no standard set of features available in a browser, some are more feature rich (Firefox) than others (Chrome). However, some features you would expect to find in a browser are: ability to alter its appearance and fonts; set a default search engine if the browser contain a search box; set a default browser for the system; export/import bookmarks from other browsers; and manage add-ons / extensions / plugins. Advanced browser features can include: email client; Usenet support; Internet Relay Chat (IRC) client; proxy settings to create an anonymous identity; private browsing so nothing is stored; and customisation of the menu or a toolbar.

One of the most important aspects of a web browser is their compatibility with web standards; web standards are maintained by the World Wide Web Consortium. The World Wide Web Consortium (W3C) was founded by Tim Berners-Lee, the inventor of the World Wide Web, and is an international standards' organisation. W3C's goal is for software vendors to adhere to their specification and standards: so that webpages will be displayed identically by each client program (browser). If a website loads correctly in one browser but not another, due to one browser not adhering to W3C standards, it is obviously a frustrating situation for the user (who can't access the content correctly) and the webmaster (who may lose the visitors business and goodwill). The most popular web browser - by historical usage share - has been Microsoft's Internet Explorer, and some versions of this browser are renowned for not compiling with W3C web standards; Internet Explorer version 6.0 being a case in point. A group of disgruntled web developers - frustrated by some browsers ignoring web standards - formed the Web Standards Project (WaSP) in 1998: the purpose of the group was "to fight" for the compliance of web standards in browsers. The WaSP has developed the Acid1, Acid2, Acid3 and Acid4 tests: these tests test how browsers comply with HTML 4, CSS 1, CSS 2, CSS 2.1, CSS 3, DOM, SVG, and EcmaScript. Update (2014): the Acid4 test is still to be created, and the WaSP group appears to be defunct.

bullet Mobile Browsers

The earliest web browsers were designed exclusively for desktop and laptop computers, and, until relatively recently (2014) this trend has continued to be the status quo. However, from the year 2000 on wards, the technology of mobile phones - also referred to as cell phones and smartphones - has advanced in 'leaps and bounds'. This has resulted in mobile phones being capable of browsing the web, and increasingly, are capable of accessing many of the services available to traditional computers.

Browser on a tablet
(Pictured: Browsers are now designed to work on mobile tablets and smartphones)

However, due to the screen size and technological limitations of mobile phones, browsers designed for desktop computers are rarely compatible with mobile devices. Therefore, a range of 'mobile browsers' have been designed: designed exclusively for mobile devices, these browsers render web content so that it can be displayed within the limitations of a mobile screen. Due to the popularity of browsing the World Wide Web with mobile phones: many websites have designed their webpages, so they will 'serve' a mobile version of the page for mobile browsers. Websites that are compatible with mobile browsers are referred to as: the mobile web.

Mobile browsers, and by extension mobile phones, typically connect to the Internet by either: 1) cellular / mobile networks; 2) wireless networks (wifi etc). Traditional browsers use HTTP (Hypertext Transfer Protocol) to retrieve webpages across the Internet; while mobile browsers support standard HTTP, they can also use the Wireless Application Protocol (WAP). Likewise, while mobile browsers can render webpages in the standard HyperText Markup Language (HTML), they usually utilises 'lightweight' webpages designed for them in markup languages, like: Handheld Device Markup Language (HDML); Wireless Markup Language (WML); and Extensible Hypertext Markup Language (XHTML). The Mobile Web Initiative (MWI) has been created by the W3C to help develop these markup languages and expand the amount of mobile devices that can access the web.

Mobile browsers typically fall into two categories: 1) default browser installed by the mobile device manufacturer; 2) user installed mobile browser. While some mobile devices allow users to remove the default browser and install another browser, many mobile devices only allow the use of the default browser. The following is a collection of popular mobile browsers: Amazon Silk, Android, BlackBerry, Blazer, Chrome, Firefox for Mobile, Internet Explorer Mobile, Kindle Basic Web, Opera Mobile, Safari Mobile, Skyfire and WebOS.

bullet Privacy Browsers

Concerns are being raised about the 'power' large tech companies exert on the Internet -- think Facebook, Amazon and Google -- and there is a growing awareness about the information these companies are collecting about the individuals who use their services. This has resulted in software being designed to protect a persons privacy whilst browsing the World Wide Web and using Internet applications. Browser extensions for virtual private network (VPN) -- TunnelBear and Windscribe have designed extensions for Google Chrome -- enable users to encrypt their browsing activity and hide their geo-location (by using the VPNs IP address). The Opera browser is now packaged with its own free VPN service; though questions have been raised about how Opera handles users usage logs; many commercial VPNs promise not to create/store an identifying log (based on IP and timestamp).

Another platform that is designed to protect users privacy whilst browsing the World Wide Web is the Tor network, which comes packaged with its own Tor browser (a modified version of Firefox). The Tor network bounces communications through three relays (hosted by volunteers), and the links between the relays are encrypted. This makes the Tor network extremely hard for eavesdroppers to read what data is sent or received through it. While it is extremely difficult to de-anonymise a Tor user, it is not impossible: one example is end-to-end timing -- watching data coming out and in to the Tor networks relays -- which may make it possible to analysis the users traffic. Some journalists have researched the development of onion routing -- what the Tor network is based upon -- and have discovered it was mostly funded by DARPA and other federal government departments of the United States. This has left a question mark hovering over how private the Tor network actually is, with no firm conclusion drawn from privacy advocates.

bullet Popular Web Browsers

Browsers for the Mac

Browsers for Linux