simulation-distance

You can change the simulation-distance of your server by going to server.properties and changing:

simulation-distance=10

To a different number, for example:

simulation-distance=5

Default value: 10

What is simulation distance?

20 times every second (every ‘tick’), the Minecraft server updates the game world. This includes things like:

• moving entities (mobs, items, players, etc)
• growing crops
• processing redstone
• spawning mobs
• …and much more

All of this processing takes CPU power. The more chunks the server has to process, the more CPU power it needs.

The simulation-distance setting controls how many chunks around each player the server will tick (i.e. update) every tick.

For example, if the simulation-distance is set to 5, the server will tick all chunks within a radius of 5 chunks around each player. Anything outside that radius won’t be updated until a player gets closer.

Recommended starting value

simulation-distance=5

The simulation distance you choose entirely depends on:

• your server’s hardware (mainly CPU)
• how many players are online at peak times
• what kind of world your server has (flat minigame/event world vs open-world SMP, for example)
• how much lag you are experiencing (or any crashes due to CPU overload)
• how important having a high simulation distance is to your players (e.g. do they build a lot of farms that stretch out to the default sim distance?)

I’d recommend starting with a value of 5, and then increasing it if your server can handle it or your players complain.

Number of chunks ticked per player

The simulation-distance is the radius of chunks around a player which are ticked. Ticked just means that the server does stuff in those chunks - like updating entities, processing redstone, growing crops, etc.

If you have it set to 10, it will tick the chunks in a square, going 10 chunks outwards in each direction (north, south, east, west) from the player. That means that there will be 20 chunks in each direction (10 chunks in one direction, and 10 chunks in the opposite direction), plus the chunk the player is standing in. That means a total of 21 chunks in each direction.
In this case, the total number of chunks ticked would be chunks.

You can calculate this as follows:

Exponential growth

From this, you can probably see that doubling the simulation distance doesn’t double the number of chunks ticked for each player, it actually quadruples it.

You need to be careful when increasing the simulation distance, because even a small increase can have a big impact on performance - especially CPU usage, as I’ll explain.

CPU effect

The simulation distance is pretty much the main setting that affects CPU usage on a Minecraft server. The more chunks the server has to tick, the more CPU power it needs.

If your server is lagging, or even crashing due to CPU overload, lowering the simulation distance is one of the best ways to reduce CPU usage. It’s not the only way, though, There can be much better optimisations depending on your server setup.

RAM effect

The simulation distance does have a big effect on RAM usage, but the main thing to think about with RAM usage is the view distance.

When the server ticks chunks, it needs to keep them loaded in RAM. The more chunks it has to tick, the more RAM it needs. But the actual chunk data (that the view distance controls) has a much bigger effect on RAM usage.

Network effect

The simulation distance is mainly all server-side. While some things are sent to the client, so it might have a small effect on network usage, it’s not as significant as the view distance.

An alternative: adaptive simulation distance

Some plugins, such as View Distance Tweaks, claim to adjust the simulation distance dynamically based on server performance.

Don’t be fooled by the name - despite being called “View Distance Tweaks”, it can also adjust the simulation distance.

If the server starts to lag, it lowers the simulation and view distance, and when the server is performing well, it increases it so that players can see further.