Browser extension

Source: Wikipedia, the free encyclopedia.

A browser extension is a software module for customizing a web browser. Browsers typically allow users to install a variety of extensions, including user interface modifications, cookie management, ad blocking, and the custom scripting and styling of web pages.[1]

Browser plug-ins are a different type of module and no longer supported by the major browsers.[2][3] One difference is that extensions are distributed as source code, while plug-ins are executables (i.e. object code).[2] The most popular browser, Google Chrome,[4] has over 100,000 extensions available[5] but stopped supporting plug-ins in 2020.[6]


Internet Explorer was the first major browser to support extensions, with the release of version 4 in 1997.[7] Firefox has supported extensions since its launch in 2004. Opera and Chrome began supporting extensions in 2009,[8] and Safari did so the following year. Microsoft Edge added extension support in 2016.[9]

API conformity

In 2015, a community group formed under the

application programming interface (API) for browser extensions.[10] While this particular work did not reach fruition,[11] every major browser now has the same or very similar API due to the popularity of Google Chrome.[4]

Chrome was the first browser with an extension API based solely on

CSS, and JavaScript. Beta testing for this capability began in 2009,[12][13] and the following year Google opened the Chrome Web Store. As of June 2012, there were 750 million total installations of extensions and other content hosted on the store.[14] In the same year, Chrome overtook Internet Explorer as the world's most popular browser,[15] and its usage share reached 60% in 2018.[16]

Because of Chrome's success, Microsoft created a very similar extension API for its Edge browser, with the goal of making it easy for Chrome extension developers to port their work to Edge.[17] But after three years Edge still had a disappointingly small market share, so Microsoft rebuilt it as a Chromium-based browser.[18][19] (Chromium is Google's open-source project that serves as the functional core of Chrome and many other browsers.) Now that Edge has the same API as Chrome, extensions can be installed directly from the Chrome Web Store.[20]

In 2015, Mozilla announced that the long-standing XUL and XPCOM extension capabilities of Firefox would be replaced with a less-permissive API very similar to Chrome's.[21] This change was enacted in 2017.[22][23] Firefox extensions are now largely compatible with their Chrome counterparts.[24]

Apple was the last major exception to this trend, but support for extensions conforming to the Chrome API was added to Safari for macOS in 2020.[25] Extensions were later enabled in the iOS version for the first time.[26]

In 2021, these browser vendors formed a new W3C community group, called WebExtensions, to "specify a model, permissions, and a common core of APIs".

Manifest V3, which greatly reduces the capability of ad blockers and privacy-related extensions.[28][29][30] Thus the WebExtensions group is viewed by some extension developers as nothing more than Google imposing its Manifest V3 design.[31][32][33]

Unwanted behavior

Browser extensions typically have access to sensitive data, such as

browsing history, and they have the ability to alter some browser settings, add user interface items, or replace website content.[34][35] As a result, there have been instances of malware, so users need to be cautious about what extensions they install.[36][37][38][39]

There have also been cases of applications installing browser extensions without the user's knowledge, making it hard for the user to uninstall the unwanted extension.[40]

Some Google Chrome extension developers have sold their extensions to third-parties who then incorporated adware.[41][42] In 2014, Google removed two such extensions from the Chrome Web Store after many users complained about unwanted pop-up ads.[43] The following year, Google acknowledged that about five percent of visits to its own websites had been altered by extensions with adware.[44][45][46]


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  2. ^ a b "Plugin". 9 September 2022. Retrieved 7 December 2022.
  3. ^ "Why Browser Plug-Ins Are Going Away and What's Replacing Them". 8 January 2014. Retrieved 6 June 2023.
  4. ^ a b "StatCounter Global Stats". StatCounter. Retrieved 11 November 2020.
  5. ^ Cimpanu, Catalin. "Half of all Google Chrome extensions have fewer than 16 installs". ZDNet. Retrieved 19 February 2021.
  6. ^ "Google Chrome 88 released: RIP Flash Player". Retrieved 29 January 2021.
  7. ^ "Browser Extensions". 15 August 2017. Retrieved 29 September 2020.
  8. ^ Edwards, Lin; "Google Chrome extensions to be officially released". Retrieved 27 April 2023.
  9. ^ Bright, Peter (18 March 2016). "Edge browser now has extensions in the latest Windows 10 preview". Ars Technica. Condé Nast.
  10. ^ "Browser Extension Community Group Charter — Browser Extension Community Group". Retrieved 14 December 2018.
  11. ^ "Re: One question from Florian Rivoal on 2017-07-29 ([email protected] from July 2017)". Retrieved 14 December 2018.
  12. ^ "Extensions Status: On the Runway, Getting Ready for Take-Off". Chromium Blog. Retrieved 14 December 2018.
  13. ^ "Extensions beta launched, with over 300 extensions!". Chromium Blog. Retrieved 14 December 2018.
  14. ^ Vikas SN (29 June 2012). "The Lowdown: Google I/O 2012 Day 2 – 310M Chrome Users, 425M Gmail & More". MediaNama. Retrieved 14 June 2013.
  15. ^ "Internet Explorer usage to plummet below 50 percent by mid-2012". 3 September 2011. Archived from the original on 20 November 2011. Retrieved 4 September 2011.
  16. ^ Statcounter. "Browser Market Share Worldwide | StatCounter Global Stats". Retrieved 20 October 2018.
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  18. ^ "Microsoft Edge: Making the web better through more open source collaboration". Windows Experience Blog. 6 December 2018. Retrieved 14 December 2018.
  19. ^ Keizer, Gregg (8 December 2018). "With move to rebuild Edge atop Google's Chromium, Microsoft raises white flag in browser war". Computerworld. Retrieved 14 December 2018.
  20. ^ "Add or remove extensions in Microsoft Edge". Microsoft. Retrieved 8 June 2020.
  21. ^ "The Future of Developing Firefox Add-ons". Mozilla Add-ons Blog. 21 August 2015. Retrieved 15 December 2018.
  22. ^ "Upcoming Changes in Compatibility Features". Mozilla Add-ons Blog. 10 August 2017. Retrieved 15 December 2018.
  23. ^ "How to enable legacy extensions in Firefox 57 - gHacks Tech News". 12 August 2017. Retrieved 14 December 2018.
  24. ^ "Porting a Google Chrome extension". Mozilla. Retrieved 30 December 2018.
  25. ^ "Safari 14 Release Notes". 2020. Archived from the original on 23 March 2022. Retrieved 4 April 2022.
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  28. ^ Barnett, Daly (9 December 2021). "Chrome Users Beware: Manifest V3 is Deceitful and Threatening". Electronic Frontier Foundation. Retrieved 22 November 2023.
  29. ^ Amadeo, Ron (1 December 2023). "Chrome's next weapon in the War on Ad Blockers: Slower extension updates". Ars Technica. Retrieved 2 December 2023.
  30. ^ "Inside the 'arms race' between YouTube and ad blockers". Engadget. 1 December 2023. Retrieved 2 December 2023.
  31. ^ Stuwe, Cuyler (29 December 2021). "Re: Do not outlaw dynamic code". GitHub. Nobody outside of Google really has any meaningful sway, since Chrome currently owns nearly all of the market share; Google sets the rules, other people nitpick minor details, and everyone pretends that everyone had a meaningful say.
  32. ^ "Re: Do not outlaw dynamic code". GitHub. 2 January 2022. Google has shown no interest whatsoever in deviating from their original plans. So, it's quite clear what's happening here. MV3 is a business decision, not an engineering decision.
  33. ^ "Re: Manifest v3 background scripts should not be killed when there are active listeners". GitHub. 7 January 2024.
  34. ^ "Protect User Privacy". Google Chrome Docs. 18 March 2018. Retrieved 15 December 2018.
  35. ^ "Add-on Policies". MDN Web Docs. Retrieved 15 December 2018.
  36. ^ "Security firm ICEBRG uncovers 4 malicious Chrome extensions - gHacks Tech News". 16 January 2018. Retrieved 15 December 2018.
  37. ^ "Google's bad track record of malicious Chrome extensions continues - gHacks Tech News". 11 May 2018. Retrieved 15 December 2018.
  38. ^ "Chrome Extension Devs Use Sneaky Landing Pages after Google Bans Inline Installs". BleepingComputer. Retrieved 15 December 2018.
  39. ^ "Google Chrome extensions with 500,000 downloads found to be malicious". Ars Technica. 17 January 2018. Retrieved 30 December 2018.
  40. ^ "PUP Criteria". Malwarebytes. Retrieved 13 February 2015.
  41. ^ "Adware vendors buy Chrome Extensions to send ad- and malware-filled updates". Ars Technica. 17 January 2014. Retrieved 20 January 2014.
  42. ^ Bruce Schneier (21 January 2014). "Adware Vendors Buy and Abuse Chrome Extensions".
  43. ^ Winkler, Rolfe (19 January 2014). "Google Removes Two Chrome Extensions Amid Ad Uproar". Wall Street Journal. Retrieved 17 March 2014.
  44. ^ "Ad Injection at Scale: Assessing Deceptive Advertisement Modifications" (PDF). Archived from the original (PDF) on 5 June 2015.
  45. IDG
  46. IDG. Archived from the original
    on 11 December 2019. Retrieved 16 June 2015.

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