The Sims Online Features: Not One Game, But Many

There is no single "The Sims Online" game currently running (the 2002–2008 MMO shut down). Instead, online features are woven across the series:

Current Online Experiences

Game	Online Features	Platform
The Sims 4 (2014–present)	Gallery (share/download Sims, lots, rooms), My Library, Multiplayer (Together Mode) — visit friend's save, control your Sim in their world (limited), EA App friends list, cross-platform saves (PC/Mac/PS/Xbox).	PC, Mac, PS4/5, Xbox One/Series
The Sims FreePlay (2011–present)	Always-online mobile. Town building, social tasks, neighbor visits, live events, competitions. Microtransactions.	iOS, Android
The Sims Mobile (2018–present)	Always-online mobile. Story-driven, heirlooms, careers, parties, fashion contests. Energy timers.	iOS, Android

The Sims Online (TSO) (2002–2008) — Subscription MMO. Private servers exist (FreeSO).
The Sims 3 Store / Exchange (2009–2018) — Web-based content sharing. Shut down; content still usable if downloaded.
The Sims 2 / 3 (Console) — No online features.

If you want a persistent shared world: FreeSO (TSO revival) or Sims 4 Together Mode (mod) — but the latter is a third-party mod (not EA).

Online Games