No downloads
What runs in the tab, and what the tab actually fetches to run it.
Nothing to install
There is no client, no launcher, and no executable. The engine is WebAssembly and it runs in the tab, inside the same sandbox as any other web page.
That also means there is nothing to uninstall, and nothing that keeps running after you close the tab.
What does get loaded
Not installing is not the same as transferring nothing. The first time you open a page that runs the engine, the browser fetches two things: the compiled engine, about 380 KB, and the game data, a 27.5 MB IWAD.
The IWAD is cached for a year and marked immutable, so it is fetched once per browser and never again, including on later visits to other pages that use it.
Both are cached. The IWAD is marked immutable for a year, so it is fetched once per browser and never again.
Why Freedoom
The game data is Freedoom, a free and redistributable IWAD that runs on the Doom engine. It means the levels can be shipped to a browser without anyone needing to own a copy of anything.
