Flatpak is a desktop-focused application distribution and deployment system for linux. This talk will walk through the technical details of the core functionallity and explain how it work and why it works that way. Flatpak has now had a major stable release and the rate of change is slowing down. This is a good time to take a look at how the things work behind the scenes. This talk will go through the technical details behind flatpak, explaining things like ostree, bubblewrap and how flatpak uses this to implement the sandbox and basic flatpak commands. It will also explain in high-level terms how the portals and other desktop integration features work.