I think you're misunderstanding that the web export isn't an EXE file. You don't upload any runnable file. What you upload is the index.html file, and the audio, data, fonts, icon, img, js, and movies folders. The web export works by having a web browser draw all the game's content, there is no executable being run to play the game online. The web browser reads the JavaScript code on the website and plays the game that way.