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.
[1][4] To provide a wide range of dynamic behavior for web pages, every major browser supports JavaScript.
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.
[7] This figure shows for various browser engines the duration of its active development, the period when relevant new web standards continue to be added to it.