I'm a bit confused about the difference between simulation distance and render distance in Minecraft (Java Edition specifically, if that matters).
From what I understand, render distance is how far you can see, but then what exactly does simulation distance affect? Does it impact mob spawning, redstone, or anything like that? Also, if I’m playing single-player, does changing one affect performance more than the other?
Render Distance
Render distance is about how far the game shows the world around you. Specifically, it determines how many chunks (16x16 block areas) are loaded visually on the client side. So if you set it to 12, you'll be able to see up to 12 chunks in every direction — forming a square 25 chunks wide (12 out, center chunk, and 12 back).
This setting only affects visuals:
Terrain, structures, and mobs beyond this range won't be visible at all.
It doesn't affect whether mobs spawn, redstone works, or crops grow — those are all handled by simulation distance.
You can verify how many chunks are loaded by pressing F3 in Java Edition. Look for "Client Chunk Cache" — it reflects your render distance.
Simulation Distance
Simulation distance controls how far from the player the game actively processes mechanics. This includes:
Mob spawning and behavior
Redstone circuits
Crop growth, furnaces, fluid movement, and other ticking systems
If something is outside the simulation range, it simply doesn’t update. For example:
A redstone clock won’t tick
A farm won’t grow anything
Mobs will freeze in place (or won’t spawn at all)
This setting is especially noticeable in single-player or when hosting a server, where you're responsible for all the game logic.
Optimizing for Performance
Render distance mostly affects your graphics performance. The more chunks the game has to draw, the harder it is on your GPU and memory.
Simulation distance impacts your CPU usage. The game has to constantly tick everything in those chunks — mobs, redstone, crops, etc.
On multiplayer servers, simulation distance is often capped server-side to reduce load. Even if you set it high, the server might ignore it.
In java edition, simulation distance decides how far chunks around the player are loaded and ticked. Specifically, it only restricts that distance (ie you can't tick chunks further than render distance).
A chunk being "ticked" means that it processes things inside it. this does include mob spawning, mob AI, redstone (though redstone can force-load chunks under certain conditions).
It has no effect in multiplayer, as that setting is decided on the server.
If you're looking for performance, turning down simulation distance can maybe help, but unless you're making really crazy things, it's not really a big factor of performance loss compared to view distance. If your graphics card is good but your CPU is terrible (we're talking pre-2010, which would be idiotic to pair with a good GPU), then it would most likely help a lot.
