Wiki software (also known as a wiki engine or wiki application) is software that runs a wiki, or a website that allows users to collaboratively create and edit web pages using a web browser. A wiki system is usually a web application that runs on one or more web servers. The content, including all current and previous revisions, is usually stored in either a file system or a database. Wiki software is a type of collaborative software.
The first wiki application was WikiWikiWeb, created by Ward Cunningham in 1994 and launched on his company's website, c2.com, in 1995.
Some wiki software, e.g. MediaWiki, stores data in a database. Other wiki software, e.g. PMWiki, stores data in flat files. The former is more scalable.
Some factors deemed important to the decision of which wiki software to use in academic settings include cost, complexity, control, clarity, common technical framework, and features. The fact that most wiki software lacks tools such as an equation editor, instant messaging, link checking, and virtual whiteboard, has been described as a limitation in their usefulness for academic work.
The primary difference between wikis and more complex types of content management systems is that wikis tend to focus on the content, at the expense of the more powerful control over layout, workflow and publishing technologies such as blogs present in other CMSes.
The majority of wikis are free and open source software developed collaboratively. Many wikis are modular, providing APIs which allow programmers to develop new features without requiring them to be familiar with the codebase.
It is hard to determine which wiki applications are the most popular, although a list of lead candidates includes Foswiki, MoinMoin, TikiWiki, XWiki, DokuWiki, and MediaWiki.
Due to the popularity of wikis, as well as the growth in complexity of wiki software, many applications exist that provide wiki functionality in addition to other standard web functionality. Many applications allow for creating blogs and discussion forums either in addition to wiki pages, or using wiki pages. A website that lets users publish blogs using wiki-style editing is known as a bliki. Some applications provide content management system functionality, also either in addition to using wiki functionality: TikiWiki is an example. In addition, applications exist that let users edit a spreadsheet in wiki style: WikiCalc is one example.