A loaded chunk is one the server is holding in memory and, usually, ticking. Understanding what causes a chunk to load explains most «why is it lagging when nobody is on» questions in one go.
What loads chunks
- A player standing there, plus everything within their view and simulation distance.
- The spawn chunks, which stay loaded whether anyone is there or not.
- A portal that a mob or item has just travelled through.
- Plugins that deliberately keep an area loaded — claims, shops, minigame arenas.
- Anything that a player or entity is being teleported to.
Spawn chunks are the surprising one
A square of chunks around the world spawn point stays loaded permanently, ticking, from the moment the server starts. Players build farms there deliberately because they keep running when nobody is online — which is exactly why an unexplained baseline load often lives at spawn.
If your server is busy with nobody on it
- Check what is at spawn
Fly there and look. Farms, redstone clocks and hopper chains built in the always-loaded area run twenty-four hours a day.
- Check plugins that force-load chunks
Anything with a «keep loaded» or «always active» option. It is a reasonable feature and it is also a permanent cost.
- Shrink the spawn area if you do not need it
Paper lets you reduce the always-loaded radius, and recent Minecraft versions expose it as a game rule. Setting it small is safe on most servers and is one of the few free wins.
/forceload add keeps a chunk ticking forever, including through restarts, and there is no notification that it is happening. Servers accumulate these. /forceload query in each world is worth running once, just to see what past-you decided.
A chunk nobody is near costs no CPU at all. This is why pregenerating terrain helps joins but does not raise your idle load, and why a world can be enormous on disk and still tick perfectly.