About this Doom browser demo
The Doom browser link opens the Emscripten demonstration provided by doomgeneric. It is a porting project and demonstration, rather than a promise of the complete commercial release. Its repository explains that the engine needs WAD game data; shareware and commercial WADs contain different content and have different distribution rights.
Controls and game data
Start with a keyboard and mouse, and check movement, strafe, fire, use and weapon selection in the destination's controls. If a loader requests a WAD, use a compatible file from a legitimate source and follow the documented filename and version requirements. An engine's availability does not mean every campaign or mod is included.
Before a longer session
Check which episode the hosted demo currently offers before committing to a campaign. Save persistence depends on the browser build's storage implementation; an in-game save is not automatically a downloadable backup. The repository is the authoritative place to check supported configurations. This listing documents the upstream project and has not completed a gameplay or save-durability test.