Most active is UO Outlands. Several thousands players?
They've reworked a lot of systems and it's basically 100x better than original UO.
There are several systems in place, which original devs wouldn't even dream of and saying that, official Ultima Online is still running. :D
It's PvP server, but with balanced PvP which really works for everyone. Not like original devs, they just dropped PvP because cookie-cutter players cried.
Outlands is impressive from a technical standpoint, they've put an insane amount of work into it and the player count speaks for itself. I played there for a while.
Personally though, I feel they've overengineered it a bit. So many custom systems layered on top that it starts to feel more like WoW with UO graphics than actual UO. The original charm was in the simplicity you, a sword, and a world that didn't care about your feelings. But that's just my taste, and clearly thousands of players disagree with me, so what do I know. And yes, the fact that official UO is still running in 2026 is both beautiful and insane
This was the bummer to me when I tried it. I liked the bug-ridden classic experience before the notoriety patch.
I recently tried https://www.classicuo.eu/ ClassicUO, and the nostalgia was incredible. Granted it is not playable, but there is something about that experience that all of the assistants, hotkeys, etc. fail to capture.
> and a world that didn't care about your feelings
Dead on.