Free and open source software, also F/OSS, FOSS, or FLOSS (for Free/Libre/Open Source Software) is software which is liberally licensed to grant the right of users to study, change, and improve its design through the availability of its source code. This approach has gained both momentum and acceptance as the potential benefits have been increasingly recognized by both individuals and corporate players.

'F/OSS' is an inclusive term generally synonymous with both free software and open source software which describe similar development models, but with differing cultures and philosophies. 'Free software' focuses on the philosophical freedoms it gives to users and 'open source' focuses on the perceived strengths of its peer-to-peer development model. However many people relate to both aspects and so 'F/OSS' is a term that can be used without particular bias towards either camp.