Guide
Fix "Can't Keep Up! Is the Server Overloaded?"
The console warning "Can't keep up! Is the server overloaded? Running Xms or Y ticks behind" means the server fell behind its 20 ticks per second for a moment.
When you can ignore it
One warning right after a start, a wake from sleep, or a big world generation burst is normal. The server catches up by itself.
When it is a real problem
If the warning repeats every few seconds while people play, blocks reappear after breaking, or mobs freeze, the server is overloaded.
Fix it
- Lower View distance and Simulation distance on Settings → Game options.
- Find the cause with spark on Paper: see How to find lag with spark.
- Pregenerate the world so exploring does not generate chunks live: Chunky guide.
- If memory is the limit, use Upgrade plan on the Overview.
More on lag
Want to try this on a real server? Campfire is free and runs Vanilla. Village adds plugins, Kingdom adds mods and modpacks.