Collaborative software, also known as groupware, is application software that integrates work on a single project by several concurrent users at separated workstations (see also computer supported cooperative work). In its modern form, it was pioneered by Lotus Software with the popular Lotus Notes application running in connection with a Lotus Domino server; some historians argue that groupware was anticipated by earlier monolithic systems such as NLS. The wiki software upon which Wikipedia runs evolved from a free software philosophy for similar collaborative applications-without the trade limitations of proprietary software or the social limitation of a hierarchy.

Software becomes more valuable when more people use it and thus Metcalfe's law applies. For example, calendaring becomes more useful when more people are connected to the same electronic calendar and choose to keep their individual calendars up-to-date.

The more general term social software applies to systems used outside the workplace, for instance, online dating services and social networks like Friendster. The study of computer-supported collaboration includes study of the software and social phenomena associated with it.