How can you know how many tabs are open in an user browser

Question

According to this post

a typical firefox user has 2-3 tabs open.

How can they say that ?

Does Mozilla receive user statistics from firefox?

Can you get this information using javascript ?

Can you get this information with other browsers ?

Answer 1

Yes, they do get certain user statistics, and I assume this is one of them. You can't access this in regular content (web page) JavaScript, in any browser, as far as I know.