Is there a way to find the active number of unique players playing NS? The only way i've been able to do so is the World Assembly but not everyone signs up for that.
As Treciene seems to hint at, themforum's "Who is online" list shows anyone viewing the forums (apart from moderators and other staff, who can hide their presence). Similarly the game's "World" page contains a "Currently online" number, but I believe that is an overestimate.
Since nations cease to exist after 28 days (or 60 on vacation mode), most existing nations are at least active enough to log in that often. Since thousands of these are puppets, the WA member list is the best way to easily filter for unique players.
If you can do some programming, the NS API has "lastactivity" and "lastlogin" shards for nations. The Daily Dumps (rather than single API queries) would be the best way to retrive this information, since they contain information on all nations in a single file; they also contain the "lastactivity" and "lastlogin" information. This is the most accurate way to filter for exactly what you need, but it requires a little programming knowledge.
RIP Residency 3.5.16-18.11.21, killed by simplistic calculation Political Compass: Economic -9.5 (Left) / Social -3.85 (Liberal) Wrote issue 1523, GA resolutions 532 and 659 meth When the people are being beaten with a stick, they are not much happier if it is called 'the People’s Stick.' — Mikhail Bakunin (to Karl Marx) You're supposed to be employing the arts of diplomacy, not the ruddy great thumping sledgehammers of diplomacy. — Ardchoille The West won the world not by the superiority of its ideas or values or religion [...] but rather by its superiority in applying organised violence. — Samuel P. Huntington (even he said that!)