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A web browser is a software application for retrieving, presenting and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier (URI) and may be a web page, image, video or other piece of content. Hyperlinks present in resources enable users easily to navigate their browsers to related resources. A web browser can also be defined as an application software or program designed to enable users to access, retrieve and view documents and other resources on the Internet.

Although browsers are primarily intended to use the World Wide Web, they can also be used to access information provided by web servers in private networks or files in file systems. The major web browsers are Chrome, Firefox, Internet Explorer, Opera, and Safari.

History

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Function

The primary purpose of a web browser is to bring information resources to the user ("retrieval" or "fetching"), allow them to view the information ("display", "rendering"), and then access other information ("navigation", "following links").

This process begins when the user inputs a Uniform Resource Locator (URL), for example http://en.wikipedia.org/, into the browser. The prefix of the URL, the Uniform Resource Identifier or URI, determines how the URL will be interpreted. The most commonly used kind of URI starts with http: and identifies a resource to be Retrieved over the Hypertext Transfer Protocol (HTTP). Many browsers also support a variety of other prefixes, such as https: for HTTPS, ftp: for the File Transfer Protocol, and file: for local files. Prefixes that the web browser cannot directly handle are often handed off to another application entirely. For example, mailto: URIs are usually passed to the user's default e-mail application, and news: URIs are passed to the user's default newsgroup reader.

In the case of http, https, file, and others, once the resource has been Retrieved the web browser will display it. HTML and associated content (image files, formatting information such as CSS, etc.) is passed to the browser's layout engine to be transformed from markup to an interactive document, a process known as "rendering". Aside from HTML, web browsers can generally display any kind of content that can be part of a web page. Most browsers can display images, audio, video, and XML files, and often have plug-ins to support Flash applications and Java applets. Upon encountering a file of an unsupported type or a file that is set up to be downloaded rather than displayed, the browser prompts the user to save the file to disk.

Information resources may contain hyperlinks to other information resources. Each link contains the URI of a resource to go to. When a link is clicked, the browser navigates to the resource indicated by the link's target URI, and the process of bringing content to the user begins again.

Features

Available web browsers range in features from minimal, text-based user interfaces with bare-bones support for HTML to rich user interfaces supporting a wide variety of file formats and protocols. Browsers which include additional components to support e-mail, Usenet news, and Internet Relay Chat (IRC), are sometimes referred to as "Internet suites" rather than merely "web browsers".

All major web browsers allow the user to open multiple information resources at the same time, either in different browser windows or in different tabs of the same window. Major browsers also include pop-up blockers to prevent unwanted windows from "popping up" without the user's consent.

Most web browsers can display a list of web pages that the user has bookmarked so that the user can quickly return to them. Bookmarks are also called "Favorites" in Internet Explorer. In addition, all major web browsers have some form of built-in web feed aggregator. In Firefox, web feeds are formatted as "live bookmarks" and behave like a folder of bookmarks corresponding to recent entries in the feed. In Opera, a more traditional feed reader is included which stores and displays the contents of the feed.

Furthermore, most browsers can be extended via plug-ins, downloadable components that provide additional features.

User interface

Most major web browsers have these user interface elements in common:

• Back and forward buttons to go back to the previous resource and forward respectively.
• A refresh or reload button to reload the current resource.
• A stop button to cancel loading the resource. In some browsers, the stop button is merged with the reload button.
• A home button to return to the user's home page.
• An address bar to input the Uniform Resource Identifier (URI) of the desired resource and display it.
• A search bar to input terms into a search engine. In some browsers, the search bar is merged with the address bar.
• A status bar to display progress in loading the resource and also the URI of links when the cursor hovers over them, and page zooming capability.

Major browsers also possess incremental find features to search within a web page.

Privacy and security

Most browsers support HTTP Secure and offer quick and easy ways to delete the web cache, cookies, and browsing history. For a comparison of the current security vulnerabilities of browsers, see comparison of web browsers.

Standards support

Early web browsers supported only a very simple version of HTML. The rapid development of proprietary web browsers led to the development of non-standard dialects of HTML, leading to problems with interoperability. Modern web browsers support a combination of standards-based and de facto HTML and XHTML, which should be rendered in the same way by all browsers.

Extensibility

A browser extension is a computer program that extends the functionality of a web browser. Every major web browser supports the development of browser extensions.

See also

• Geobrowsing
• List of web browsers
• Mobile browser
• Timeline of web browsers
• Web browser history
• Web browser (layout) engines

References

1. Jacobs, Ian (15 December 2004). "URI/Resource Relationships". Architecture of the World Wide Web, Volume One. World Wide Web Consortium. Retrieved 30 June 2009. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
2. "Browser". Mashable. Retrieved 2 September 2011.
3. "Browser Information". DBF. Retrieved 7 June 2012.
4. "The SeaMonkey Project". Mozilla Foundation. 7 November 2008. Retrieved 30 June 2009.
5. "Cyberdog: Welcome to the 'doghouse!". 5 July 2009. Retrieved 30 June 2009.
6. Teelucksingh, Dev Anand. "Interesting DOS programs". Opus Networkx. Retrieved 30 June 2009.
7. Andersen, Starr (15 September 2004). "Part 5: Enhanced Browsing Security". Changes to Functionality in Microsoft Windows XP Service Pack 2. Microsoft. Retrieved 30 June 2009. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
8. "Pop-up blocker". Mozilla Foundation. Retrieved 30 June 2009.
9. "Safari: Using The Pop-Up Blocker". Mac Tips and Tricks. WeHostMacs. 2004. Retrieved 30 June 2009.
10. "Simple settings". Opera Tutorials. Opera Software. Retrieved 30 June 2009.
11. Bokma, John. "Mozilla Firefox: RSS and Live Bookmarks". Retrieved 30 June 2009.
12. "RSS newsfeeds in Opera Mail". Opera Software. Retrieved 30 June 2009.
13. "About Browsers and their Features". SpiritWorks Software Development. Retrieved 5 May 2009.

External links

• Architecture of the World Wide Web, Volume One
• WorldWideWeb: Proposal for a HyperText Project
• How Browsers Work: Behind the scenes of modern web browsers
• Existing browsers

• Use dmy dates from October 2012
• Web browsers