Rendering refers to the visual representation of a model that initially exists as a collection of data and will only be displayed as a picture, an image or a video sequence in high resolution through the process of rendering.

General information

Starting from a model that is still shown on the generating computer with rudimentary information, rendering requires complex calculations to illustrate the intricacies of this model adequately. These calculations include the shapes, colors, and surface textures. The generating computer translates certain information, such as the viewer’s perspective, the appearance of surfaces, as well as light and shadows distribution in a 2D or 3D model, which will then look real at the end of the rendering process.

Types function

A distinction is made between pre-rendering and real-time rendering. The former takes quite a lot of computing power to complete, as it is trying to make the generated images, graphics or videos appear very close to reality. One application is film production. Real-time rendering on the other hand, is used in applications, where the activity of the viewer or user plays an important role. For example, in video games and for websites.[1]

The visual reproduction of HTML is referred to as rendering. Because HTML is a description of a text, initially no visual representation is specified as part of it. HTML can be displayed independent of the screen in other media such as projectors, LCD, and other display devices. The reason for this is that HTML as a markup language only determines the content structure of the text and not its way of presentation. How HTML is ultimately shown, is usually specified with CSSs (Cascading Style Sheets). The CSS elements specify for individual structural parts of an HTML document how they are to be presented by providing options for formatting and colors for the text elements. The time required for a browser to display an HTML document is also referred to as a render time, however, loading time is the more common term.

Relevance to SEO

The loading time or render time of a webpage is an important SEO criterion, since it shows whether a website has good performance or not. 1 to 3 seconds is the general average standard for all content to be loaded. If this time is greater, it is highly likely that users will exit the site. A long loading time results in a high bounce rate and short visitor stay on the site, both important characteristics that Google most likely uses in their assessment of websites. Various measures can be undertaken to keep the loading time as short as possible. For example, modification of the infrastructure by using a CDN or the “slimming” of the source code using valid HTML code and the outsourcing of certain files such as CSS or JavaScript.

Google also recommends the use of a rendering program to verify the crawlability of a website. A crawler cannot imitate the rendering of a webpage. Therefore, a text-based renderer such as Lynx should be used to make sure the crawler can read or parse a website. Lynx renders a site exactly as a crawler would do it, but is fundamentally different from a graphics-based rendering program, which is used in browsers.[2] In Mozilla Firefox this is, for example, Gecko, while Safari and Chrome use Webkit, and Internet Explorer uses Trident or Tasman.


  1. Rendering. Accessed on 01/22/2014
  2. Webmaster Guidelines. Accessed on 01/22/2014

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