itch.io

HTML files have .html extentions

Also most game engines give Index.html as the game file.

NOTE: sometimes the game won't work in your browser, don't worry , it is not the problem with your game in most cases

it is because of a feature is new browsers which prevent it from playing the file unless, the game is played from a server like itch's server.

So after hosting the game in itch it should work