FOSDEM stands for the Free and Open Source Software Developers’ European Meeting. It is a large, volunteer-run gathering held in Brussels, Belgium, traditionally on the ULB Solbosch campus over a weekend. The event has run since 2001 and has become one of the most important meeting points for the European and global free-software communities. Its own site for the 2026 edition advertises thousands of attendees, hundreds of lectures, and dozens of developer rooms.
The FOSDEM 2026 page sets the event at the ULB Solbosch Campus on January 31 and February 1, 2026, and describes the scale plainly in terms of “8000+ hackers,” “65 devrooms,” “1013 lectures,” and lightning talks. The “devroom” model is a signature of FOSDEM: individual projects and communities are given rooms to run their own mini-conferences in parallel, so a single weekend hosts everything from kernel and toolchain discussions to language-specific and special-interest tracks.
A defining characteristic of FOSDEM is that admission is free and registration is not required. There is no ticket gate and no paywall, which keeps the event open to students, hobbyists, and professionals alike. This free-admission policy is deliberate and aligns the conference with the values of the software it celebrates: the meeting is organized by volunteers and supported by the community rather than run as a commercial trade show.
FOSDEM functions as a kind of annual town square for open source. Maintainers who collaborate online all year meet face to face, projects coordinate roadmaps, and newcomers get a dense, low-cost introduction to the breadth of the ecosystem. The sheer number of parallel tracks means the event documents, in one weekend, much of the activity across the free and open-source world.
As a community institution, FOSDEM belongs alongside the other gatherings in this library: the language-focused PyCon, the hacker-culture events such as the Chaos Communication Congress and DEF CON, and the broader movements of free software and open source whose developers fill its rooms.