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A web browser engine is a computer program that renders web pages. This is the process of transforming HTML documents into a graphical representation on a computer monitor. For instance, this Wikipedia article had to be rendered by a browser engine in order to read it on a PC, phone, or other electronic device.

Similar to the engine of a car, a browser engine is not a stand-alone entity that can operate by itself. Rather, it is a core component of larger programs, primarily web browsers.


Name and scopeEdit

There is not a single term for browser engines. They can be referred to as a layout engine, a rendering engine, or a combination of these.[1][2][3]

During the early years of the Web in the 1990s, there was modest use of JavaScript (JS) compared to today. As the use of JS expanded, the JS interpreters in browsers matured into distinctly separate engines. Thus, to properly render and execute a web application, the two engines must work in concert, which is accomplished via the Document Object Model.

For example, the Firefox browser has both the Gecko layout engine and the SpiderMonkey JS engine. Likewise, the Google Chrome browser has the Blink and V8 engines.

The focus of this article is on the traditional layout engine.

Additional informationEdit

The spatial layout of a web page on an electronic display is typically stipulated by Cascading Style Sheets (CSS). This includes the rendering of text using different fonts.

Some layout engines may begin rendering before all of a web page's resources are downloaded. This can result in visual changes as more data is received, such as images being gradually filled in or a flash of unstyled content.

Layout engines can be embedded in programs besides web browsers, such as an email client that renders HTML email or an EPUB e-book reader. (JavaScript engines have also been embedded in other programs, e.g. V8 in Node.js and SpiderMonkey in GNOME 3.)


Browser usage on Wikipedia during February 2014
Google Chrome, Opera and other variants (Blink)
Internet Explorer (Trident)
Firefox and other variants (Gecko)
Safari and other variants (WebKit)
Opera (Presto)
Non-mobile web browser usage for Wikimedia visitors during February 2014.[4]

Trident is the layout engine of Internet Explorer, also used by Microsoft Outlook and other Windows applications. Microsoft now uses the newer EdgeHTML engine in its Edge browser.

Gecko is the Mozilla project's layout engine, used by the Firefox browser, the Thunderbird email client, and the SeaMonkey internet suite. Goanna is a fork of Gecko used by the Pale Moon browser.

KDE created the KHTML engine for use in its Konqueror browser. Apple forked KHTML to make the WebKit engine for its Safari browser. Google originally used WebKit for its Chrome browser but now uses its own fork called Blink. The Opera browser also uses Blink; previously, it used its own Presto engine.



See alsoEdit


  1. ^ "Gecko". Mozilla. Retrieved 2018-04-21. 
  2. ^ "Behind the scenes of modern web browsers". Tali Garsiel. Retrieved 2018-04-21. 
  3. ^ "Introducing Goanna". M.C. Straver. 2015-06-22. Retrieved 2018-04-21. 
  4. ^ Wikimedia Traffic Analysis Report - Browsers e.a.: Monthly requests or daily averages, for period: 1 Feb 2014 - 28 Feb 2014, Wikimedia