View distance vs simulation distance: which one to lower to reduce lag

Both settings are in server.properties, both are measured in chunks (16 blocks), and both default to 10. They sound alike but do different jobs, which is why lowering the wrong one does little for lag.

What it looks like in a Spark report

In a Spark report, look for most of the server thread's time under entities, machines and chunk ticking, and for the Entities and Chunks lines on the timeline climbing as MSPT climbs. Your current values are shown in the Configurations section of the details panel, so you can see what you are starting from.

If the time is mostly entities, mobs or machines, simulation distance is the setting that changes it. If you have many players spread out over the world, view distance matters more, because the server loads and sends chunks around each of them.

What each setting does

Simulation distance decides how far from each player entities, crops and machines keep running. Inside it, mobs move, crops grow and redstone works. Beyond it, the chunk is still there but nothing in it is ticking.

View distance is how many chunks the server loads and sends to each player. It decides how far players can see. Terrain beyond the simulation distance but inside the view distance is still drawn, but it is frozen: mobs stand still and crops do not grow.

That is why simulation distance is the one that cuts server work. Fewer chunks ticking means fewer things to do each tick, and players rarely notice a change of 1 or 2.

How to choose

• Time mostly in entities, mobs or machines: lower simulation distance.
• Many players spread out, lots of chunk loading: lower view distance a little as well.
• Not sure: start with simulation distance, then take a new profile.

Either way, change one setting, by 1 or 2, then restart and take a new profile. That is the only way to know which one helped.

What to lower, in order

Check it worked

Take a new profile once the server has been up for a while, with the lag happening, and compare the median and 95th percentile MSPT with your old one. If they came down, keep the change. If nothing moved, the cause is elsewhere. See how to read a Spark report, and what “Can't keep up” means if that is the message you are seeing.

What to leave alone

• Cutting view distance hard to fix tick lag. It mostly changes how far players see and how much the server sends, so the saving is usually small.
• Changing both settings at once, or by a lot. Change one by 1 or 2, restart, and take a new profile.
• Lowering simulation distance so far that farms and machines stop where players use them. Beyond it, crops do not grow and redstone does not run.

Common questions