Until this release, Scope could only count people who had signed in. Most people never do — the extension works without an account, which is the point — so the number we had was not the number of people using Scope. It was the number of people using Scope who had also bothered to log in, which is a different and much less useful question.
Scope now sends a short "someone is using this" ping. It contains four things: a random number generated on your device, which product it is, which platform, and the version.
What it never contains: what you searched for, which pages you visited, course names, file names, anything you read, anything you wrote, or where you are.
The random install ID is not derived from your device, your hardware, your browser, or your account. It is not shared with anyone and it is not used to build a profile. If you happen to be signed in, the ping is linked to your account — not to learn more about you, but so that using Scope on your laptop and your desktop counts as one person instead of two.
The part we care most about getting right is what "active" means. A browser extension is technically running the whole time Chrome is open, so a ping on a timer would report every install as active every day and the number would be worthless — flattering and worthless. So the ping fires when you actually do something: open Scope, search, land on a course page. Stop, and it goes quiet within about fifteen minutes. Idle time does not count.
This is the whole of it. There is no second system, no analytics vendor, and nothing sold. The full table is in the extension's privacy documentation.