A persistent world (PW) is a multiplayer server whose setting, characters and story continue permanently, rather than resetting after each session. Players log in and out at will; the world and the other characters in it keep existing, and keep changing, whether or not any one player is online.
The term is used mainly in the Neverwinter Nights community, but the idea is closer to a long-running tabletop campaign than a typical online game: a shared setting, a cast of Dungeon Masters, and a story that is written collectively, over months or years, by the people playing it.
Compared to other options
A persistent world vs. a module vs. an MMO
- A module
- A single map or short adventure, usually played once with a small, fixed group. When it ends, it ends - there's no ongoing setting to return to.
- A persistent world
- An always-on server with a continuing setting. Characters live on a server vault, DMs can intervene directly in the story, and new players can join an existing world at any time.
- An MMO
- A commercial game built around large populations, instanced content and a studio-written story that applies to every player the same way. A PW is run by volunteers on one small server, with a story that individual players can actually change.
What they tend to have
Common features of a PW
A server vault
Characters are stored on the server rather than the player's own install, so progress persists between sessions and machines.
Active Dungeon Masters
Volunteer DMs run events, control NPCs live and respond to what players actually do, rather than following a fixed script.
An original or expanded setting
Many PWs build their own pantheon, regions and history rather than running an official campaign setting as-is.
Community rules
Level caps, PvP policy, and what's allowed in character creation are set by the server's own team, not by the base game.
An example
Auldwyn is a persistent world
Auldwyn runs on NWN:EE with its own pantheon, regions and story, a volunteer DM team, and a server vault. It's live now and growing level by level, from 1 up to a planned cap of 40.