How to Find and Fix Lag

Server lag is the ultimate fun-killer. Whether it’s "ghost blocks" that reappear after you break them or mobs that teleport around, no one likes a slow world. Let’s walk through a systematic way to find the root cause and get your server back to a smooth 20 TPS.

1. What Kind of Lag Is It?

Before you can fix it, you need to know what you’re fighting:

Server Lag (TPS): The server itself is slow. This is the most common kind. Mobs move in slow motion and blocks take a second to drop items.
Network Lag (Ping): The server is fine, but the connection is slow. Players will "rubberband" or get kicked. Check the Network stats in Mission Control.
Client Lag (FPS): This isn't the server's fault; it's the player's computer struggling to render something (like 5000 item frames in one room).

2. The "Quick Fix" Checklist

Try these in order to see if you get an instant improvement:

The Item Sweep: Run /minecraft:kill @e[type=item] (Careful: this deletes items on the ground!). If the lag disappears, someone likely had a broken farm spilling items everywhere.
Run a Profile: Don't guess. Use Spark for 5 minutes to see exactly which plugin is eating your CPU.
The Half-and-Half Test: If the lag is constant, disable half your plugins. If the lag stops, the problem is in that half. Repeat until you find the winner.

3. The Usual Suspects

1. Too Many Mobs (Collision Lag)

If you have a farm with 200 cows in a 1x1 hole, the server has to do thousands of math problems every second to see if they're touching. The Fix: Thin out your farms and make sure your max-entity-cramming gamerule is set to something reasonable like 24.

2. Redstone Clocks

A "rapid clock" fast-ticking circuit forces the server to calculate lighting and block updates multiple times every single second. The Fix: Use slower clocks or integrated circuit mods like Create.

3. Flying with Elytra

Moving fast into new, ungenerated chunks is the #1 cause of temporary lag spikes. The Fix: Pre-generate your world and drop your view distance slightly.

Still feeling the stutter? Our Discord community is great at reading profiling reports. Drop your link in #support!