Portal:Free and open-source software

Free and open-source software (FOSS) is software available under a license that gives users the right to use, share, modify, and distribute the software – modified or not – to everyone and provides the means to exercise those rights using the software's source code. FOSS is an inclusive umbrella term encompassing free software and open-source software. The rights guaranteed by FOSS originate from the "Four Essential Freedoms" of The Free Software Definition and the criteria of The Open Source Definition. All FOSS has publicly available source code, but not all source-available software is FOSS. FOSS is the opposite of proprietary software, which is licensed restrictively or has undisclosed source code.

The historical precursor to FOSS was the hobbyist and academic public domain software ecosystem of the 1960s to 1980s. Free and open-source operating systems such as Linux distributions and descendants of BSD are widely used, powering millions of servers, desktops, smartphones, and other devices. Free-software licenses and open-source licenses have been adopted by many software packages. Reasons for using FOSS include decreased software costs, increased security against malware, stability, privacy, opportunities for educational usage, and giving users more control over their own hardware.

The free software movement and the open-source software movement are online social movements behind widespread production, adoption and promotion of FOSS, with the former preferring to use the equivalent term free/libre and open-source software. FOSS is supported by a loosely associated movement of multiple organizations, foundations, communities and individuals who share basic philosophical perspectives and collaborate practically, but may diverge in detail questions. (More about free and open-source software...)

Alternative terms for free software, such as OSS, FOSS, and FLOSS, have been a recurring issue among free and open-source software users from the late 1990s onwards. These terms share almost identical licence criteria and development practices.

In 1983 Richard Stallman launched the free software movement and founded the Free Software Foundation to promote the movement and to publish its own definition. Others have published alternative definitions of free software, notably the Debian Free Software Guidelines. In 1998, Bruce Perens and Eric S. Raymond began a campaign to market open-source software and founded the Open Source Initiative, which espoused different goals and a different philosophy from Stallman's. (Full article...)

• ... that the International Criminal Court decided to switch from Microsoft Office to OpenDesk after its chief prosecutor was disconnected from his Microsoft-hosted email account? (2026-03-01)
• ... that Terry Davis created TempleOS, a Bible-themed operating system that had more than 120,000 lines of code? (2025-03-20)
• ... that the browser extension AdNauseam blocks and clicks on advertisements at the same time? (2025-01-06)
• ... that Riley Testut developed AltStore because he wanted to publish his emulator Delta? (2024-06-01)
• ... that you can keep a snowflake in a browser tab? (2022-11-08)
• ... that Kotaku revised an article about Nintendo Switch emulation after Nintendo complained that the previous version encouraged piracy? (2022-10-17)
• ... that Vegeta is used to attack HTTP-based applications? (2022-09-11)

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Wikipedia is an encyclopedia written entirely by volunteers. If you wish to contribute to our articles, feel free to join the free and open-source task force. To find a place to start, you can expand a stub or improve existing articles. To pick an existing article, you could choose from the list of most-viewed FOSS articles or a vital article about free and open-source software. The vital articles are listed below with their current content assessment rating: