I have my mob farm. It is 23 blocks above the ground.

I stayed at the bottom of it, but no mobs are spawning. After leaving and exploring a nearby cave, 2 zombies spawned.

My question is, do mobs only spawn with a x/z radius, not y?

Reference to my world: https://drive.google.com/file/d/11mI8T22wTDw-8Z1MqMSb9sA98DDMaxyT/view

  • I should brush up on it but I think Minecraft has a spawn system that tries to not spawn a mob on you so if you were right there, it will not spawn probably within a 5-10 blocks from you. So if you were right there waiting for a spwn it might be that.
    – Fredy31
    Commented May 26, 2021 at 19:53
  • but is there any flaws with my xp farm? Note there is 2 floors @Fredy31
    – Coder2195
    Commented May 26, 2021 at 19:56
  • 1
    You basically just need to not be right there looking at it for it to work.
    – Fredy31
    Commented May 26, 2021 at 19:59

2 Answers 2


The mob cap may be the issue

Each time Minecraft attempts to spawn a mob, it will check if it is below the mob cap. Other zombies and creatures are spawning inside caves or dark places and take up the mob cap.


  • rebuilding the farm above an ocean (there will be no caves) (also the easiest)
  • lighting up all the caves below the farm
  • afking 100 blocks above the farm, so that you only load the chunks the farm is in (160 worked best for me)

The design of the mob farm can also be an issue. Farms that rely on passive wandering (random walking around) are fairly slow (in my experience). The most efficient kinds of mob farms use some sort of water to push the mobs down.

This one works very well for me:

(might need to switch it up a little bit as it relies on QC and it doesn't work in BE)

  • It did work, but only after the doing adventures in the nether, so it prob not design
    – Coder2195
    Commented May 28, 2021 at 16:03
  • @Coder2195 its probably the mob cap then
    – giilbert
    Commented May 28, 2021 at 16:09
  • Then shall I build 100 blocks above?
    – Coder2195
    Commented May 28, 2021 at 16:13
  • I think that'll work, but building it in on top of a deep ocean or lighting the up caves would be better
    – giilbert
    Commented May 28, 2021 at 16:16
  • it is near a deep ocean
    – Coder2195
    Commented May 28, 2021 at 16:16

From the wiki: https://minecraft.wiki/w/Spawn

Mobs spawn naturally within a square group of chunks centered on the player, 15×15 chunks (240×240 blocks). When there are multiple players, mobs can spawn within the given distance of any of them.

and later

Spawn conditions

Whether a spawn condition fails differs from the above determination if the game tries to spawn them in that biome. For example, dolphins can have pack spawns that occur inside of frozen ocean and deep frozen ocean biomes, but no other biomes. These rules apply to variants of the same mob, such as baby zombies and spider jockeys.

Each individual spawn attempt succeeds only if all of the following conditions are met:

There must be no players or the world spawn point within a 24 radius block distance (spherical) of the spawning block


So basically, mobs can spawn within a radius of about 120 blocks in any direction, but not within 24 blocks of you.

  • Aha spherical thats the answer I needed
    – Coder2195
    Commented May 26, 2021 at 20:00
  • but i went far and wide and stayed there for a bit, but it didn't work could you check for flaws and conduct some tests?
    – Coder2195
    Commented May 26, 2021 at 20:02
  • A thing that is important to note is... nothing was developped in Minecraft vanilla (without mods) to help with mob farms. So you have 2 things that make it difficult: be too close, the mobs wont spawn. Go too far, the mobs are despawned (so even if they were there, they are removed by the game). So yeah its rough, to make a mob spawner work you need to stay between the two rings that I talked about and stay there always. Go to a mine just a little too far? boom, your mobs in the farm are gone so you reset from 0
    – Fredy31
    Commented May 27, 2021 at 18:54
  • could you send me a copy of the map I linked with the areas best for standing highlighted with red wool?
    – Coder2195
    Commented May 27, 2021 at 20:00

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