As with all recent Forza titles, there’s a Forza Horizon 3 Demo available right before the game’s September 27 release. Microsoft didn’t make an official announcement, but there’s a store page for the demo announcing the release date of September 11 at 8 PM Eastern, only on Xbox One. It’s not live yet at the time of this post, but it will be very soon.
The download size is 18.34GB. While the demo is not launching on the Windows 10 store, the game itself is releasing on September 27 on both Xbox One and Windows 10 PCs.