A browser engine (also known as a layout engine or rendering engine) is a core software component of every major web browser. The primary job of a browser engine is to transform HTML documents and other resources of a web page into an interactive visual representation on a user's device.
Besides "browser engine", two other related terms are commonly used: "layout engine" and "rendering engine".[1] [2] [3] In theory, layout and rendering (or "painting") could be handled by different engines. In practice, however, these components are tightly coupled and rarely encountered on their own outside of the browser engine.[1]
In addition to layout and rendering, a browser engine enforces the security policy between documents, handles navigation through hyperlinks and data submitted through forms, and implements the Document Object Model (DOM) exposed to scripts associated with the document.[1] [4]
Every major browser supports JavaScript to provide a wide range of dynamic behavior for web pages. However, JavaScript is implemented as a separate JavaScript engine, which has enabled its usage elsewhere. In a browser, the two engines are coordinated via the DOM and Web IDL bindings.[4]
Browser engines are also used in non-browser applications. An email client needs one to display HTML email. Beginning in the 2010s, many apps have been created with the frameworks based on Google's Chromium project; each of these standalone apps functions much like a web app. (Two examples are Spotify and Slack.)[5] [6]
The layout of a web page is typically specified by Cascading Style Sheets (CSS). Each style sheet is a series of rules for how the page should be presented. For example, some rules specify typography details, such as font, color, and text size, while others determine the placement of images. The engine combines all relevant CSS rules to calculate precise graphical coordinates for the visual representation it will paint on the screen.[1] [4]
Some engines may begin rendering before a 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.[7]
Only the duration of active development is shown, which is when relevant new Web standards continue to be added to the engine.
ImageSize = width:750 height:170PlotArea = left:80 right:5 bottom:20 top:5AlignBars = justifyDateFormat = dd/mm/yyyyPeriod = from:01/01/1997 till:31/05/2022TimeAxis = orientation:horizontal format:yyyy
Colors = id:microsoft value:rgb(0.3, 0.5, 1) id:gecko value:rgb(1, 0, 0) id:khtml value:rgb(0.3,0.3,0.3) id:webkit value:rgb(0.3, 0.36, 0.36) id:blink value:rgb(0.3, 0.39, 0.39) id:mgray value:rgb(0.5, 0.5, 0.5) id:lgray value:rgb(0.75, 0.75, 0.75)
ScaleMajor = gridcolor:mgray unit:year increment:1 start:01/01/1997ScaleMinor = unit:month increment:3 start:01/01/1997BackgroundColors = bars:lgray
BarData = bar:Gecko text:Gecko bar:Trident text:Trident bar:EdgeHTML text:EdgeHTML bar:KHTML text:KHTML bar:WebKit text:WebKit bar:Blink text:Blink
PlotData= align:center textcolor:black fontsize:8 mark:(line,black) width:15 shift:(0,-4)
bar:Gecko from: 01/05/1997 till: 31/05/2022 color:gecko mark:(line,white)
bar:Trident from: 01/10/1997 till: 15/07/2015 color:microsoft mark:(line,white)
bar:EdgeHTML from: 12/11/2014 till: 15/12/2018 color:microsoft mark:(line,white)
bar:KHTML from: 04/11/1998 till: 15/10/2016 color:khtml mark:(line,white)
bar:WebKit from: 25/06/2001 till: 31/05/2022 color:webkit mark:(line,white)
bar:Blink from: 03/04/2013 till: 31/05/2022 color:blink mark:(line,white)