You can now play the original Devil (and its expansion, Hellfire) in virtually any web browser on any computer with generally excellent performance and controls that work as expected. It's all thanks to an open source project published on GitHub called Diabloweb , which is now being distributed by game developers on X.
In the README file on the project's GitHub repository, the project's developer (d07RiV) notes that it is based on DevilutionX, another open source project that has done a lot of work to Devil work well on modern operating systems.
“I modified the code to remove all dependencies and exposed the minimal required interface with JS, allowing the game to be compiled in WebAssembly,” d07RiV writes. “Event handling (especially in the menus) had to be modified significantly to fit the JS model.”
It's pretty simple to set up: just go to the website, upload a file, and you're good to go.
You need to upload a file because the project is Devil game files: you need to save these in the form of the DIABDAT.MPQ file in the Devil installation folder.
There are three ways above that you can source this MPQ file. First, you can of course own a physical copy of the original game. Alternatively, you can purchase the game from GOG and install it, then extract the file from the installation directory.
There is also a shareware release of Devil, and you can get the SPAWN.MPQ file from there, and it works fine. That's not the full game though, so that's more if you just want to try it out.
I played the game for about half an hour using the MPQ from the GOG version, without any issues on Firefox on a Mac. (There is no Mac version of the GOG installer, however, so I had to run the installer in a Windows virtual machine to get to the file.) The game is clearly primitive compared to more recent entries in the series (or even Diablo II), but it's an addictive game to play regardless.