Wikipedia mirrors

From Wikinfo

There are numerous Wikipedia mirrors, websites that mirror Wikipedia content word-for-word, on the World Wide Web. This is due to the open nature of the GNU Free Documentation License (GFDL), under which Wikipedia has been released, which allows literally anyone to replicate and even modify and redistribute Wikipedia content.

The only caveat is that the adapted works must include both the full text of the GFDL as well as provide access to the original work, which in this case would be the Wikipedia website. On the Web, this is done by providing a link back to the original article. Thus, for every article that a website adapts or mirrors, a link is provided to the original article on Wikipedia.

An inadvertent side-effect of this practice - also known as "Google bombing" - has resulted in vastly increased page rankings in search engines to the point where Wikipedia is now one of the most visited sites on the Web.

The most complete compendium of these mirrors is here, which includes annotations about license issues with each site.

There are mixed feelings at Wikipedia about these copies. Many are mere copies, to generate advertising traffic; the copies may become dated, which is a concern. Some copies are partial sub-sets of limited subject areas. In many cases there are concerns that the GFDL license terms are not being followed; many of these site are unstable, and don't last long.

In some cases, the articles are copied to save them from deletion. This is called forking; see for example How Comixpedia forked from Wikipedia.

On a technical level, mirroring of the complete contents of Wikipedia is greatly facilitated by online availability of large data files that contain the complete set of articles, and optionally include associated history and talk contents.