Following the Uncovered: Final Fantasy XV event, Square Enix made the Platinum Demo available for PS4 and Xbox One.
The indicated download size is 3.5 gigabytes on PS4 and 4.5 on Xbox One. Below you can read a short blurb explaining what we can expect from the experience:
“PLATINUM DEMO — FINAL FANTASY XV whisks players away to a fragmented dreamscape, introducing an original story with a few unique twists. Join young Noctis and his magical guide as you explore the fantastical world of his dreams.”