How to reduce lag on a Minecraft server

Only the first one is about the server. The server runs at 20 ticks per second (TPS). Each tick has 50 milliseconds; when a tick takes longer, the server falls behind and the whole world slows down for everyone.

The Server health card in the Console tab shows it without any plugin: 20.0 when all is well, or how many ticks the server fell behind the last time it could not keep up.

The Performance card on the Overview tab shows CPU, Memory and Players over the last day or week, so you can see whether the lag comes with more players or with memory at the top.

spark is a free profiler that shows exactly what the server spends its time on. It is available as a plugin for Paper and as a mod for Fabric, Forge and NeoForge.

1. Install spark from the Plugins or Mods tab and restart.
2. When the lag happens, type /spark tps. It shows TPS and MSPT, the milliseconds per tick. Under 50 MSPT is healthy.
3. Start a profile with /spark profiler start, let it run for two or three minutes while the lag is there, then /spark profiler stop.
4. spark gives a link to a report. Open it and expand the biggest entries: they tell you whether entities, chunk loading, redstone or a plugin eats the time.

A spark report is a tree of everything the server thread did, with the share of time each part took. Open the biggest branch under the server tick and look for one of these:

Run the profiler while the lag is actually there. A report from a quiet moment shows a healthy server and sends you looking in the wrong place.

These two settings in server.properties have the biggest effect of anything you can change, and they do different things.

• view-distance is how far players can see. Chunks in that range are sent to players but not simulated.
• simulation-distance is how far around each player the world is alive: mobs move, crops grow, redstone runs.

Simulation is the expensive part. Lowering simulation-distance to 6 while keeping view-distance at 10 keeps the view the same and takes a large load off the server. Players only notice that farms far away from them stop running, which they do in singleplayer too.

Paper and Spigot have settings that vanilla does not, and a few of them make a clear difference on a busy server. Change one at a time and restart after each change.

Each of these changes the game slightly, so tell your players. Server.properties explained shows where these files sit next to server.properties.

In most spark reports on busy survival servers, entities are at the top: mobs, dropped items, minecarts and item frames. Common causes:

• Mob farms that collect hundreds of animals or villagers in one place.
• Item farms without a collection system, so thousands of items lie on the ground.
• Large animal pens. Cows and chickens tick like any mob.

Talk to the owners of big farms first. On Paper, config/paper-world-defaults.yml also has limits, for example on how many entities can push into each other, and bukkit.yml controls how many mobs spawn per player.

Some builds cost tick time all day, also when nobody uses them. These are the ones to look for after a spark report points at entities or block entities.

• Hopper chains: every hopper checks for items many times a second. Long lines of hoppers under a storage system add up; water streams or minecarts with hoppers carry items more cheaply.
• Redstone clocks that run all the time, often left behind in an old farm. Ask players to put a lever on each clock so it can be turned off.
• Villager trading halls with dozens of villagers. Each villager thinks about paths and jobs; locking them in one block cells keeps that work down.
• Piles of item frames, armor stands and minecarts in one area, such as a decorated shop street.

To find where entities pile up on Paper, type paper entity list in the console. It counts every entity type per world, and adding a type, such as paper entity list minecraft:item, shows the chunks where that type gathers.

Generating new terrain is one of the heaviest things a server does. When players explore in different directions on a fresh world, TPS drops. Generating the area in advance, while nobody plays, removes that cost. Pre-generate your world shows how, straight from the World tab.

• On vanilla? Switch to Paper in Settings. It is the same game with much better performance, and the world stays as it is.
• On Fabric? Add performance mods such as Lithium and FerriteCore. They change nothing about gameplay.
• Heavy plugins: if spark points at one plugin, look for a lighter alternative or check its settings. Plugins that scan the whole world, like some anti cheat or map plugins, can be heavy.

If spark shows 20 TPS and players still complain, look at their side. High ping comes from distance and the player's own connection; a player far away from the server always has more delay. Low FPS is solved on the player's computer, for example with the Sodium mod, lower render distance, or closing other programs.

Minecraft runs the world on one main thread, so the speed of a single core matters most. That is why our servers run on the AMD Ryzen 9 7950X, which boosts to 5.7 GHz. Extra cores still help: world generation, chunk loading, garbage collection and many plugins work next to the main thread.

When the CPU graph on the Overview tab stays at the top during play, while the settings on this page are already in order, the server needs more processor. Extra vCPU can be added when you configure a server.

1. Check the Server health card: is the TPS below 20 while people play?
2. Look at the memory and CPU graphs on the Overview tab during the lag.
3. Run a spark profile while the lag is there and open the biggest branch.
4. Set simulation-distance to 6 and keep view-distance at 10.
5. Count the entities, and talk to the owners of the biggest farms.
6. Pre-generate the world inside a world border.
7. Run Paper or Purpur, or Lithium and FerriteCore on Fabric, and go through the Paper settings above.
8. Replace or reconfigure the plugin or mod that spark points at.
9. Only then look at more memory or more vCPU.