"In/on the App Store"

Solution 1:

The Apple App store is not a physical store but an online one, so we use on in the same way we say on the internet.

Solution 2:

It seems to me that this question is not about English grammar or usage, but about commercial product presentation and audience psychology.

The accepted answer suggests that the use of ‘on’ reflects established usage in a particular context, but I find the comparison with reference to general media (on the Internet) rather strained. I find ‘in’ more natural in these circumstances:

You can by this in Walmart

You can by this in the store

So I think it justified to consider the psychology behind what I believe is Apple’s deliberate use of on?

One possibility was to avoid the implication that one had to get up off the couch and drive to a physical location, and go into a physical store to purchase this “magical experience”.

A second, mundane, possibility is that Apple did not wish confusion with its bricks-and-mortar stores: you might try or buy a device in the Apple Store, but not on it. Using ‘on’ with the App Store when it was first launched, emphasized that it was something different.

Consistent with this suggested concern for distinguishing the App Store from the Apple Store, the official badge has now been changed, replacing “Available” by ”Download”:

(And the choice of on was not so outlandish, in the sense that a shop assistant might say ”You can find it over there, sir, on the shelf by the…”.)