Internet Guide Logo

What is a Web Browser


The World Wide Web is a service found on the Internet, and is based upon a client-server model. The World Wide Web is a hypertext document system that is based on a client-server model: a client (browser) requests and retrieves documents from servers (computers) connected to the Internet.

Browsers use URLs (Uniform Resource Identifier's) to locate documents (webpages) stored on servers: a URL is a string of characters that identify an Internet resource. Alongside locating and retrieving documents (webpages), browsers also render and display the document and can also (potentially) interact with it.

Browsers can access and navigate (also known as surfing) the World Wide Web through a number of means:

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 URL is inputted into a browser: the browser uses the Hypertext Transfer Protocol (HTTP) to validate and access the document (webpage). HTTP will request the help of TCP (Transmission Control Protocol) to retrieve the document (webpage) located at the server the URL suggests it is at.

Documents (webpages) located on the World Wide Web are designed using HTML (HyperText Markup Language). HTML is a hypertext language that uses elements to "build" a document. Browsers render HTML elements differently; therefore, a webpage will not look identical in every browser.


In 1990, the first web browser was developed by Tim Berners-Lee, and released publicly in 1991: when the World Wide Web was launched on the 6th of August, 1991. Berners-Lee invented the World Wide Web while he worked at CERN (a European center for physics research). The name of Berners-Lee's browser was 'WorldWideWeb'.

The WorldWideWeb was a basic text only browser, and, by 1992, a range of browsers were being developed to improve upon it's functionality and platform compatibility. 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 obtain widespread popularity was NCSA Mosaic. Mosaic was designed at the National Center for Supercomputing Applications (NCSA), and, by a team of software engineers that included Marc Andreessen and Eric Bina. Mosaic is acclaimed for helping to popularise the web. 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 first released on Unix? In the early 1990's the Internet was only just beginning to be commercially deregulated and most households (in developed nations) did not have access to the Internet. Therefore, operating systems, like Windows, did not focus heavily on encouraging network access. From 1990-1994, Unix was the most popular operating system, used, to access the Internet.

However, by the mid 1990's, interest in the Internet expanded, and many commercial Internet Service Providers began offering access to home users. Due to Windows being the dominant domestic operating system: the vast majority of home users connected to the Internet using Windows instead of Unix. This trend has continued to the present day (2014), and has resulted in software developers primarily designing browsers for the Windows platform.

Due to the success of Mosaic, the Mosaic Communications Corporation was created on the 4th of April, 1994. The Mosaic Communications Corporation hired the majority of software engineers who helped to design 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.

In the mid-1990s, the Netscape Navigator was the most popular browser, but, the Netscape Communications Corporation would soon be embroiled in a fierce battle with Microsoft, who released Internet Explorer and packaged it 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 has been the dominant web browser used by Windows computers. Apple released the Safari browser in 2003, and this browser, likewise, has been the dominant web browser used by Macintosh computers. While browsers have been released for other platforms - Unix, Linux, Amiga - they are niche browsers in terms of overall usage share (combined under 2% of overall browser usage).

Present Day (2014-Onwards)

Since 2010, Internet Explorer faced stiff competition from a selection of three new browsers: Opera, Chrome, and Firefox. As of 2014, 'rough' estimates of browser usage are:

  1. Chrome: 30%
  2. Internet Explorer: 22%
  3. Firefox: 19%
  4. Safari: 15%
  5. Opera: 6%
  6. Android: 5%
  7. Others: 3%

Mozilla Firefox and Google Chrome are the two browsers that have eaten into Microsoft's market share. The two ongoing criticisms of Internet Explorer have been it's size and security flaws. What is notable about the above numbers: is that browsers designed principally for the Windows and Macintosh platforms continue to monopolise web surfing.

However, it is interesting to note that Android (a browser developed for mobile devices) has taken a sizable market share. From 2014 onwards, many technology experts are predicting that mobile devices - and therefore mobile browsers - will continue to increase 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.

While web browsers make a point of being compatible with the majority of web content, they are not exclusively cross platform. The earliest web browsers were primarily compatible with Unix: in the early 1990's, Unix was the most popular operating system for Internet users. As Internet usage expanded in the 1990's, the majority of Internet users were using Windows instead of Unix: therefore, software developers began to focus on developing browsers for Windows instead of Unix.

Browser Development

While browsers are usually designed and targeted for a specific platform (operating system) they are typically written in the C++ programming language.

  1. Chrome - written in C/C++, Python
  2. Firefox - written in C/C++
  3. Internet Explorer- written in C++
  4. Opera - written in C++
  5. Safari - written in C++ and Objective-C

Since the early 1990's, the features available in browsers have steadily evolved. 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

The characteristics of the Mosaic GUI - with it's URL address bar, history manager, tools - is still maintained by modern browsers. It is generally accepted that Netscape Navigator and Internet Explorer copied the layout and features of Mosaic; however, that is to be expected with Netscape Navigator, as it was developed by the same team of developers that created Mosaic - Marc Andreessen et al.

One of the important dates in browser development is the 23rd of February, 1998: this is the day that Netscape created Mozilla. 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.

Browser Functions and Features

Web browsers tend to include the following standard features (menu bar).

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 primarily function of a web browser is to fetch and retrieve web content (webpages). Therefore, it comes as no surprise that the features highlighted above primarily deal with locating web content. Browsers locate web content using a Uniform Resource Locator (URL), and URL's are used within the three features shown above.

Browsers support a range of fonts; the default font is usually: Arial. Browsers support a range of plug-ins, the most obvious of which is: toolbars. A toobar is an additional menu, embedded in the browser, that provides easy access to an Internet service. Google's toolbar, for example, helps block unwanted popup adverts.

Browsers support advanced features - usually hidden deeper within the browser - like: accessing proxy servers; controlling Internet content for children; and setting privacy options. The primary features of a browser locate web content, and the advanced features dictate how that content is accessed and rendered.

For browsers to run optimally, their cache of data needs to be periodically deleted. There is a range of third party software that automatically deletes: temporary Internet files; saved passwords; cookies; recently types URLs; history of accessed URLs; last download locations and website icons.

Browser Compatibility: Web Standards

An important aspect of web browsers is their compatibility with web standards; web standards are recommended by the World Wide Web Consortium. The World Wide Web Consortium (W3C), founded by Tim Berners-Lee, the inventor of the World Wide Web: is an international standards organisation for the World Wide Web. Webpages are designed in HTML, the specification of which is managed by the W3C. W3C attempts to enforce software vendors to adhere to their specification and standards: so that webpages will be displayed identically by each client program (browser).

While it is not essential - for users - that a webpage renders identically in each web browser; it is important for web developers. If a web developer designs a website that does not load correctly in one browser: then the website may lose visitors and potential customers. The most popular web browser - by 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. At present (2014), the Acid4 test is still to be created; WaSP is defunct, as of 2013, so it may never be created.

Mobile Browsers

The first 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 onwards, 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 all of the services available to traditional computers.

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: mobile 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 utilise '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.

Popular Web Browsers

Browsers for the Mac

Browsers for Linux