User blog comment:Brandon Rhea/Wiki Modernization: Videos on Mobile Devices/@comment-168424-20170517205212/@comment-168424-20170518173544

From what I can tell, there is no reliable way to tell if a user is on wi-fi...

http://caniuse.com/#search=network%20information%20api

This makes the statement about only enabling auto-play on wi-fi very suspicious... especially if it doesn't work in Community Apps which can at least use a native iOS or Android API.