fog of war on mobile

No, the apps don't directly support variants, other than 960.

Thanks

So, where and how can I play the fog of war chess variant? 

@free-de.. I am unable to find that option, how do you navigate to it on the website? 

Use a mobile browser and the variants are under Play > Variants

Fog of war chess can be played on your mobile using a browser 

The chess.com app itself does not support a lot of the variants, however, you can access any of the variants on your mobile device through a Web browser. 

So only browser?

It is possible to use variants on mobile devices, (thanks to Paulsafo for this method) Here's the link to the forum page that he wrote it on (Have to scroll down to find it) https://www.chess.com/forum/view/chess-variants/how-to-play-variants-on-app

Something he did not state is that when viewing all the variants, click the "4 player and more" and it will show you more, and you can play against different players.

If you're going through all that, it's just better to use a mobile browser. That method is an embedded browser within the app so it's another layer and may not work very well.