After the reveal of Fortnite: Battle Royale for mobile, the questions started coming in. And we have answers to two of the big ones: just how robust will the cross-platform play be, and will there be controller support" While there's a ton of questions still to be answered, Epic Games provided answers to these two burning questions.
For cross-platform play and progress, it is absolutely 100% possible for someone playing the desktop or PS4 version of the game to play with a mobile player. But that is only if a person from a squad invites a friend from another platform. So a PC player with their keyboard and mouse will never play in the mobile queue. But, if a PC player invites a mobile player, then they'll play in the PC queue. It's actually the exact same way that the system functions between desktop and PS4 console players right now.
It's opt in. A PC gamer cannot join a mobile queue, but a mobile gamer can opt in to play with a PC player. They're not all dumped into one matchmaking pool. Make sense"
— Nick Chester (@nickchester) March 9, 2018

This means that mobile players don't have to worry about having to face down some keyboard and mouse champs unless they specifically join up with PC players. But what about controllers on mobile" Epic Games said to us about controller support: "Not initially. Bluetooth controller support is coming later." This means that yes, you'll be able to use your MFi controllers to play Fortnite on your...