Diclaimer: All the people who attended FOSDEM on our behalf are co-authors of this article.
In 2024, a group of people, coordinated by Pedro Bessa , decided to visit FOSDEM to start efforts to get more connected with the Open Source and Free Software communities.
This year, we decided to do more than simply attend the event. Pedro, together with Cristián Maureira-Fredes and Fabian Kosmale , sat together and applied for a stand so we could represent the Qt Project at FOSDEM.
To our delight, we got selected! And here is our detailed report of everything that we witnessed at FOSDEM 2025.
(From left to right: Unknown person, Emilia Valkonen-Damjanovic, Pedro Bessa, Cristián Maureira-Fredes, Sami Shalayel and Moss Heim. Aku Pietikäinen and Dimitrios Apostolou are missing in the picture.)
Qt Project and Qt Group
The Qt Project is an open collaboration effort to coordinate the development of the Qt software framework. Historically, most Qt Project maintainers and approvers have been part of the company that holds the right to commercial licenses but also supports the project by paying developers, infrastructure, and many other things. In this case, Qt Group (FKA The Qt Company) has that role.
Having a separate Open Source entity is particularly good because it gives the opportunity to approach diverse groups of people and visit diverse types of events, depending on if such events have a community focus or a more commercial side to them. In this case, FOSDEM gave us the chance to approach an exceptionally large portion of the community and ecosystem, as this is the biggest Open Source and Free Software event in Europe.
The venue and event magnitude
FOSDEM was expecting more than 8000 people to visit the Campus du Solbosch of the Université Libre de Bruxelles. The event used seven buildings from the campus (picture below); a massive area, filled with people having discussions everywhere.
Surprisingly, you could see that their organizational decisions regarding spaces worked very well. For example, there was a campus street packed with food trucks with diverse types of food (although heavy in gluten) and drinks, for people to have lunch. Additionally, there was a cafeteria, and a couple of other points where coffee and drinks were sold.
As with many other events, FOSDEM volunteers had their own type/color of t-shirt, so it was quite easy to find them. In fact, it was rare to be in a place without volunteers around; we could rest assured there would always be someone available to support attendees and stand organizers.
There were 88 stands distributed across 6 buildings, so we were truly fortunate to be selected as one of them. So, let us talk about stands.
Stands at FOSDEM
You can see the full list of stands here. The Qt Project booth was in building K (1st floor), and we were lucky to have our booth next to the cloak room, meaning everyone with suitcases or jackets passed through it. It certainly helped us getting a lot of attention.
FOSDEM is a good connecting networking possibility where visitors want to meet the people behind a project, so projects usually try to send in as many people as possible and alternate them through the two days. Visitors then pass multiple times at their favorite booth to try to meet more people behind their favorite project. (yes, we had some people coming over and over again!).
We were particularly interested in projects using Qt, and yes, they were many!
There was an impressive number of projects using Qt at the event, so we were fortunate to have this opportunity to visit their stands and have a chat with them.
Some of them were:
- Overte (huge interactive 3d world using Qt5 for the UI. It seems they are working on migrating to Qt6)
- Linux on Mobile (showcasing smartwatches built with Qt)
- FreeCAD (they demoed the 3D parametric modeler, using Qt)
- GNURadio (showcasing their project and their UI built with Qt)
- VideoLAN (showcasing VLC Player, built with Qt)
- KDE (several demos built with Qt: Steam Deck, Krita, Plasma Mobile, and Plasma Desktop)
- LibreOffice (they are also using Qt)
- LadyBird (new browser development using Qt for its UI)
(If I forgot to mention your project, please poke me: pedro.bessa@qt.io)
Talks at FOSDEM
Here are some of our talk highlights:
“Where Have the Women of Tech History Gone? 2.0”
In this talk Laura Durieux built on a previous talk about women in computer science by presenting on even more women from tech history. Included Sophie Wilson, a co-designer of the ARM architecture, and Radia Perlman, who invented the spanning-tree protocol foundational for the world wide web, and who also wrote a very lovely poemabout it.
“Profile-Guided Optimization (PGO) in LLVM: Current Challenges from the Adopter Perspective”
Alexander Zaitsev discussed common obstacles to using PGO in C++ projects, such as lack of documentation, misinformation and bad advice, lack of build tool support, and reproducibility. He presented the Awesome PGO project which shows some demonstrations of PGO used in real applications.
SBOM devroom
One of Sunday’s tracks was Software Bill of Materials (SBOM), which had several talks relevant to Qt’s recent work in that area. Some interesting finds were the SCANOSS projects for helping with SBOM creation and management and the OSV-Scalibr project which helps with binary scanning and vulnerability detection and management. In “Struggles with Making SBOMs for C Apps”, Chris Swan noted some rays of hope such as Yocto and Zephyr making progress on generating SBOMs for projects built on their tools, and mainstream linux distros beginning to ship SBOMs. He also pointed to a blog post he authored with more information.
Containers devroom
On Saturday, Philip Laine presented an interesting project to help in distributing container images efficiently without bottlenecking container registry. The project uses a peer-to-peer network where container downloaders also work as uploaders.
Testing and Continuous Delivery devroom
Leveraging AI to combat flaky tests with CANNIER was presented by Daniel Hiller. The presentation introduced the CANNIER approach, designed to minimize the time spent rerunning tests.
Ladybird lightning talk
Have you heard of the new browser-from-scratch called Ladybird? It uses Qt for its UI.
Find out more in their lightning talk.
Interactions at the Qt Project booth
Most of the discussion started with a “Oh, Qt! I used Qt for a project in ...” so we were a familiar project for most attendees, however we had cases with people that were completely new to our dear framework and were at least direct into asking “What is Qt?”, to which we rapidly started to give examples of Qt interfaces in the wild, which helped us to get the discussion started. We were quick to introduce them to Qt Academy and to tell them how to get started with their learning journeys. This was shown in the number of new Academy users, as during the weekend, we got close to 600 new users to Qt Academy.
Even if it was a Developer-focused event, there were a few people with other professions, like Project Managers, Families attending because another member of their family wanted to go, Marketing folks, and even random people who were curious about what was going on in the university.
We asked the visitors what kind of projects they did with Qt, and some of the highlights included Qt milking cows, Qt processing food orders and Qt tricking speed radars.
The psychological Qt social experiment
Confused by this title? Do not be! We were discussing ideas on how to encourage interactions in the booth (after all, we were competing with many others!) and decided to attract people's input in an unconventional way:
We had three candy bowls, and we labeled them with the options “C++, Python and Rust” so when people were looking at them, it was a particularly good conversation starter, because they wanted to make a statement by picking a candy from their favorite labeled candy bowl. The results of the first day were obvious, the Python bowl was empty fast, followed by a tie situation between Rust and C++.
We got a few comments like “What about language X?” so we thought of including more options for the following day.
On the second day, we decided to expand a bit the options, to attract even more people so we wrote down “Python, C++, Other (tell us!)” which was even more helpful because we managed to get into discussions about:
- Why language X is better than others
- How great would it be to have Qt support for language X
- Why language X was the best option for a certain industry
We took notes (pen and paper!) of all the other languages that were mentioned, but we are certain we lost some data due to the large amount of people at the booth, and the results were the following:
Our top languages (behind C++ and Python) were:
- Rust with 18 votes
- Go with 11 votes
- C and JavaScript with 9 votes
In total, 4.5 Kg of sweets were used for the voting during the two days.
Surprised by the results?
FOSDEM: The Perfect Offline Community Management Platform
“You are finally here!” - said many when approaching the booth, raising their voice pitch when enunciating “finally”. They had that look in their eyes as if they were getting some groceries and just bumped into their best friend from middle school.
Coinciding with Qt’s 30-year anniversary, this was our first-ever formal presence at FOSDEM with a stand representingthe Qt Project – you are welcome btw. This opportunity gave us the chance to witness people’s passion and admiration for Qt as a framework, an enabling library, an amazing tool to learn and build GUI projects.
Having a stand at FOSDEM made it easy for people to come directly to us and engage - many were eager to share their Qt stories. Some used it during uni, others for personal projects, and some were even in the process of convincing their managers to adopt Qt at work. Our presence also signals to the open source ecosystem that we are open tocollaboration – and it attracted some to come to our booth and start conversations.
Hearing users’ experiences first-hand is one opportunity to understand how important Qt is to our community. People left our booth after a good conversation with a smile, and hopefully the Qt stand memory stayed as one of their FOSDEM’s highlights.
Thank you so much for visiting our booth, being part of our community and for reading this long blog post!
And a special thanks to the volunteer team running FOSDEM, this is a really incredible event so congratulations for everyone involved!
🔗 Relevant links:
