Layout engine

A web browser's layout engine takes content (HTML, XML, images, etc.) and formatting information (Cascading Style Sheets, etc.) and computes a visual representation of the web page, usually for output on either a monitor or a printer.

All web browsers necessarily include some form of layout engine. However, the term "layout engine" only reached popular usage when the Mozilla project designed its web browser's layout engine as a component that was separable from the browser. In other words, the Mozilla layout engine (Gecko) was reusable for web browsers besides Mozilla, and so people began to refer to Gecko as a distinct "layout engine" rather than merely a part of the web browser.

Examples of layout engines include the following:

• Gecko layout engine
• KHTML