Open-source software is computer software that is available in source code form: the source code and certain other rights normally reserved for copyright holders are provided under asoftware license that permits users to study, change, improve and at times also to distribute the software.

Open source software is very often developed in a public, collaborative manner. Open-source software is the most prominent example of open-source development and often compared to (technically defined) user-generated content or (legally defined) open content movements.

A report by the Standish Group states that adoption of open-source software models has resulted in savings of about $60 billion per year to consumers

The Open Source Definition is used by the Open Source Initiative to determine whether or not a software license can be considered open source.

The definition was based on the Debian Free Software Guidelines, written and adapted primarily by Bruce Perens. They are by no means definitive even as applied to software. Clause 3 is the primary legal difference between free software andopen source software as such, free software is stricter in interpreting 3. Clauses 5 and 6 are not a condition of any major open content license regimes, which commonly do restrict types of uses and users; for instance, Creative Commonshas open content licenses that explicitly forbid commercial use.