I've spent almost 10 hours in single player putting together a mob grinder and lighting up nearby caves. Until very recently the mob grinder was working perfectly - mobs would spawn and get sucked into the kill mechanism.

During the build I have been switching between "Peaceful" and "Hard" settings to let me build in peace.

Very recently the hostile mobs stopped spawning - I've got the setting on "Hard", have started and stopped the game, switched between Peaceful/Hard, and gone on long expeditions both overland and underground.

I have not seen or heard any hostile mobs but have come across neutral mobs (even chickens deep underground).

Has anyone experienced this? I've looked at this question: No hostile mobs spawning in minecraft - but it seems to only apply to multi-player/ Minecraft servers rather than single player.

Thanks in advance for any advice.

4 Answers 4


It's a known bug, please see the Mojang bug tracker under https://bugs.mojang.com/browse/MC-42053

  • Thank you @Herjemine - I wouldn't of considered my i7 ultrabook as a low/mid spec machine but this fits exactly with my experience! Feb 26, 2014 at 3:34

After a bit of searching on the web/ forums this issue seems to be connected to version 1.7.4

I launched my world on 1.7.2. and the hostile mobs are spawning again.


While I do not sit on the exact details, I do remember that there has to be quite dark in the mob spawner, it also has to be enough space for the mobs to spawn. Mobs never spawn within X number of blocks either, so if you are within this area that can be an issue. Same if you are too far, I think that was outside maximum view distance. If you've switched between peaceful and hard often, it might have bugged the world. To test this you can build the spawner in creative mode while always on hard, and see what happens then. I don't believe there was any difference in spawn behavior of mobs in creative compared to survival, only thing is the usual hostile mobs will not be hostile unless attacked.

Mobs will never move unless you are within 32 blocks, I think this was also the same as minimal spawn distance from player. Note that I talk hostile mobs here, friendly/neutral like chickens may spawn wherever if I remember correctly.

Another possible criteria I recall is that (some) mobs may not spawn on certain blocks, biomes and heights.

It's hard to give a straight, conclusive answer to your issue, as many criteria have to click in order for those spawners to work, it seems.

  • The mobs were previously spawning in my mob spawner, and I haven't seen a hostile mob in over an hour of game play underground. Which suggests a "bugged world" - what is that and can I fix it? Feb 18, 2014 at 18:38

I'm In minecraft 1.8 and i built a mob grinder and I got only six mobs. I read a blog and it said that in 1.8 mob spawning is 10 times lower than 1.7.10.


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