Browser extension

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A browser extension is a computer program that extends the functionality of a web browser in some way. Depending on the browser and the version, the term may be distinct from similar terms such as plug-in or add-on. Extensions can be created through use of web technologies such as HTML, JavaScript, and CSS.[1] Browser extensions can also improve the user interface of the web browser with out directly affecting viewable content of a web page. This improvement can be achieved through a variety of add ons such as toolbars and plug-ins.


Microsoft Internet Explorer started supporting extensions from version 5 released in 1999.[2] Mozilla Firefox has supported extensions since its launch in 2004. The Opera desktop web browser supported extensions from version 10 released in 2009. Google Chrome started supporting extensions from version 4 released in 2010. The Apple Safari web browser started supporting native extensions from version 5 released in 2010. The syntax for extensions may be quite different from browser to browser, or at least enough different that an extension working on a browser does not work on another one. As for search engine tools, an attempt to bypass this problem is the multitag strategy proposed by the project Mycroft, a database of search engine addons working on different browsers.[3]

Most popular extensions[edit]

The following is a table of the top ten most popular extensions for Google Chrome,[4] Mozilla Firefox,[5] and Apple Safari.[6] Popularity is measured by the number of downloads for each extension.

Rank Google Chrome Mozilla Firefox Safari
1 AdBlock AdBlock Plus AdBlock
2 AdBlock Plus Video DownloadHelper Exposer
3 Lightning Newtab Firebug Facebook Photo Zoom
4 Bang5Tao - Shopping assistant NoScript Security Suite ClickToFlash
5 Iminent Greasemonkey Awesome Screenshot
6 Google Mail Checker DownThemAll! TwitterTranslate
7 Evernote Web Clipper Microsoft .NET Framework Assistant Facebook Cleaner
8 Google Hangouts FlashGot Mass Downloader Turn Off the Lights
9 Quick Start Flash Video Downloader - Full HD Download Videos for YouTube™
10 Google Translate Web Of Trust - WOT 1-Click Weather for Safari


Ad and script blockers give you control over your browsing experience. They can block ads on the sites you visit and kill third-party scripts and widgets that collect and send your data out. AdBlock Plus blocks banner ads, pop-up ads, rollover ads, and more. It stops you from visiting known malware-hosting domains, and also disables third-party tracking cookies and scripts.[7]


Main article: Browser toolbar

A browser toolbar is a toolbar that resides within a browser's window. All major web browsers provide support to browser toolbar development as a way to extend the browser's GUI and functionality. Browser toolbars are considered to be a particular kind of browser extensions that present a toolbar. Browser toolbars are specific to each browser, which means that a toolbar working on a browser does not work on another one.


Main article: Plug-in (computing)

Plug-ins add specific abilities into browsers using application programming interfaces (APIs) allowing third parties to create plug-ins that interact with the browser. The original API was NPAPI, but subsequently Google introduced the PPAPI interface in Chrome. in addition, plug-ins allow browser extensions to perform tasks such as blocking ads, creating a secure online connection, and adding applications with in a browser.


Browser extensions can help protect your online privacy far beyond the private browsing feature available on most browsers. There are many types of extensions that can be used to control various aspects of your browsing privacy and can mitigate threats. Most of the browser extensions related to privacy fall into three groups: extensions that prevent third parties from tracking your movements, extensions that block ads and scripts, and passive security tools that enforce good habits.[8]


Browser extension development is the actual creation of an extension for a specific browser. Each browser type has its own architecture and APIs to build the extensions which requires different code and skills for each extension. Nowadays there are development frameworks which allows developers to build cross-browser extensions with only one code base and one API, eliminating the need to develop a different extension version for each one of the Browsers. Examples of those frameworks are Add-ons Framework which allows developer to build cross browser extensions for Internet Explorer, Firefox, Chrome, Safari and Opera,[9] and the Crossrider development framework which allows developers to build cross browser extensions for Internet Explorer, Firefox, Chrome and Safari.[10]

Extension Maker [11] is another one interesting tool for cross browser extensions development. Opposite above two, you don't need to write any code. You can develop an extension from preexisting blocks.


In January 2014, Google removed two extensions from its browser service Chrome due to violations of its own terms of service. The decision to remove the two extensions, "Add to Feedly" and "Tweet This Page", arose after users noticed these extensions allowed unwanted pop up ads.[12]

See also[edit]


  1. ^ "What are extensions?". Retrieved 18 February 2014. 
  2. ^ "Browser Extensions". Retrieved 2010-06-05. 
  3. ^ "Mycroft project". Retrieved 2011-10-27. 
  4. ^ "Chrome Web Store". Retrieved 15 March 2014. 
  5. ^ "Mozilla Firefox Add-ons". Retrieved 15 March 2014. 
  6. ^ "Safari Extensions". Retrieved 15 March 2014. 
  7. ^ "LifeHacker". Retrieved 4 April 2013. 
  8. ^ "LifeHacker". Retrieved 4-04-13.  Check date values in: |accessdate= (help)
  9. ^ "Add-ons Framework". Retrieved 19 December 2013. 
  10. ^ "Crossrider". Retrieved 28 April 2013. 
  11. ^ "Extension Maker". Retrieved 13 October 2013. 
  12. ^ Winkler, Rolfe. "Google Removes Two Chrome Extensions Amid Ad Uproar". Wall Street Journal. Retrieved 17 March 2014. 

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