iPad Pro (9.7-inch, 10.5-inch, and both generations of 12.9-inch)
iPad Air and iPad Air 2
iPad mini 2, 3, and 4
iPod Touch (sixth-gen)
You can update your supported iDevice by going to Settings, General and Software Update. The update to iOS 12 is around 2GB but this may differ.
iOS 12 brings Camera Effects, better Augmented Reality, Screen Time, Grouped Notifications, a more advanced Do Not Disturb function, Photo Sharing, Photo Search, Memoji for the iPhone X and so much more!