The Wikimedia Commons (also called “Commons” or “Wikicommons”) is a repository of free content images, sound and other multimedia files. It is a project of the Wikimedia Foundation. Files uploaded to this repository can be used like locally uploaded files on all other projects on the Wikimedia servers, including Wikipedia, Wikibooks and Wikinews. The project was proposed in March 2004 and launched on September 7, 2004. A key motivation behind the set-up of a central repository was a desire to reduce duplication of effort across the Wikimedia projects and languages, because before the Commons was created the same file had to be uploaded to many different wikis separately.

The possibility of local uploads still exists, but is meant to be used primarily for material which local project policies allow, but which would not be permitted according to the licensing policy of the Commons, such as fair use content. As of 2005, the Wikimedia Commons itself does not allow fair use or uploads under non-free licenses, including licenses which restrict commercial use of materials. Licenses that are acceptable include the GNU Free Documentation License, Creative Commons licenses with no restrictions on use, and the public domain.

Given its primary function as a supporting project for the other Wikimedia web sites, the main content policy for files uploaded to the Commons is that they must be potentially useful on any of the Wikimedia projects. This excludes material such as purely personal pictures and artwork, in contrast to image-sharing repositories like Flickr and DeviantART. Nevertheless, large numbers of files hosted on the Commons are not used directly on any Wikimedia project and likely never will be; as such, the project has grown into a repository of multimedia in its own right, which is frequently linked to from articles on Wikipedia and other Wikimedia websites to provide supplemental materials.

The project has grown very rapidly since its inception. On May 24, 2005, it reached a milestone of 100,000 uploaded media files (excluding thousands of weather and market data images for Wikinews). It was also the first Wikimedia project to use MediaWiki 1.4. The default language for the Commons is English, but the interface can be configured (in user preferences) to use any other language. Some pages have also been translated into various languages.

Files on the Wikimedia Commons are categorized using MediaWiki’s category system. In addition, they are often collected on individual topical gallery pages. As of May 2005, many different collections can be isolated: more than 10,000 public domain paintings from ancient to modern times, 7,733 pronunciation files in various languages, hundreds of public domain recordings of classical music, and a growing collection of short videos.

From: Wikipedia. The Free Encyclopedia http://en.wikipedia.org/wiki/Wikimedia_Commons