Google Glass is not, and never was, AR

When I see people talk about head-mounted products which sport AR ("augmented reality") functionality, such as the recently announced Apple Vision Pro, I see them frequently mention Google Glass as an early entry into the AR device space. This is absolute nonsense.

Google Glass does not provide any augmented reality features. All it is, and has been, is a second screen. By the functionality it provides the wearer, it's in a similar category to smart watches.

For something to be an augmented reality device, it has to augment reality. That means adding things to one's perception of the world that aren't really there, or removing things that are. This requires anchoring (eg. visually) the augmentation to a relative position in the real world.

Google Glass just provides a second screen, a kind of HUD (head-up display) that can show information. Thanks to its camera, this may even be related to what is in front of the wearer. However, the information may be derived from the world, but the design of the hardware - the position of the screen - means it cannot augment the world.

Just because information is presented on a transparent screen, does not make it AR. Otherwise, stencilling the name of a restaurant on its window would also count as AR. Or those mirrors with the little moustache drawn on them.

None of these are augmenting reality - they just are reality.