1.18 billion daily active users on average for September 2016
1.09 billion mobile daily active users on average for September 2016
1.79 billion monthly active users as of September 30, 2016
1.66 billion mobile monthly active users as of September 30, 2016
If I visit a news site with a "share on facebook" widget which uses a facebook endpoint to get my facebook identity, am I an active facebook user?
If I have the mobile app installed which runs in the background getting notifications I never read, am I an active facebook user?
"We define a monthly active user as a registered Facebook user who logged in and visited Facebook through our website or a mobile device, or used our Messenger app (and is also a registered Facebook user), in the last 30 days as of the date of measurement."
'The social network said in an email to SocialTimes that it “wanted to provide a cleaner metric,” so starting with its third-quarter-2015 earnings report, it no longer counts what it called “third-party pings,” or people who did not access Facebook itself, but shared content or activity via Facebook Login-integrated websites or applications.'
That's exactly what is under discussion: whether FB conservatively excludes 3rd-party widgets and such when counting activity. They started being more conservative late last year.