Mobs Not Spawning on Your Minecraft Server: Monsters, Animals and Farms That Don't Work

First: the difficulty

On peaceful no monster spawns, and the ones that were there disappear. It's the first thing to check, because a new server may come like that or someone changed it to build in peace.

With the server running, type difficulty in the “Console”: it tells you the current difficulty. To change it, difficulty normal (or easy, or hard). It applies at once and is saved with the world.

1. Or from the NapNodes panel

   Inside your server, “Settings”: under “The game”, choose the “Difficulty”. With the server running it changes at once; with it stopped, it only applies to a new world, so do it while it's running.

The game rules that turn mobs off

Three rules (/gamerule) decide whether mobs spawn, and any of them may have been left on false after setting up a building world or a minigame:

spawn_mobs: whether mobs spawn on their own, animals and monsters. On false none do, except from spawners. Before 1.21.11 it was called doMobSpawning.

spawn_monsters: monsters only. Since 1.21.9 it's a game rule: spawn-monsters in server.properties is no longer read, so changing it there does nothing.

spawner_blocks_work: whether spawners work (the ones in dungeons and in farms).

To see how each one is set, type its name without a value in the “Console” (gamerule spawn_monsters), and to change it, with the value (gamerule spawn_monsters true). If your server is older than 1.21.11, use the old names (the list of rules, with the old and new names).

gamerule spawn_mobs true
gamerule spawn_monsters true
gamerule spawner_blocks_work true
difficulty normal

1. From the panel

   In “Settings”, scroll down to “Game rules” → “Mobs”: “Spawn mobs”, “Spawn Monsters” and “Enable Spawner Blocks”. Rules are changed with the server running, and the panel sets them in the Overworld, the Nether and the End at once.

Light and place: where a monster can spawn

Since 1.18, in the Overworld monsters only spawn where the block light level is 0: a torch, a lamp or nearby lava is enough to stop them. That's why a well-lit area around your base has no monsters, and why farms have to be completely dark. On the surface, it also has to be night or out of reach of skylight.

They don't spawn on glass, bottom slabs, carpets, leaves or transparent blocks either, nor where they don't fit (most need two blocks of air). There are biomes where monsters never spawn: mushroom fields and the deep dark, where only the Warden comes out when you make noise.

Animals are different: almost all of them are created when the terrain is generated, and after that they respawn very rarely and only on grass blocks with light. In an old world there are none left around the bases, and that's normal: it's not a server bug.

Distance: only near a player

Mobs only spawn around players: never closer than 24 blocks to anyone, and at most about 128 away (8 chunks; in spigot.yml, mob-spawn-range: 8). A monster that ends up more than 128 blocks from everyone despawns at once, and beyond 32 it may despawn at any time. With nobody online, nothing spawns.

Also, only in the chunks the server is “simulating”. If you lowered the “Simulation distance” a lot to reduce lag (3 or 4), the ring where mobs can spawn gets very small, because anything under 24 blocks doesn't count. With 6, which is what we recommend in the Paper optimization guide, there's still plenty of room. In the panel it's in “Settings” → “Performance”.

Spawners only activate with a player 16 blocks away or closer. A spawner farm needs someone next to it; having the chunk loaded isn't enough.

The mob cap is full (the most common one)

Minecraft has a cap on mobs per category. On Paper, by default, 70 monsters, 10 animals, 15 bats and others for fish and axolotls (spawn-limits in bukkit.yml), and each player has their own cap (per-player-mob-spawns: true in config/paper-world-defaults.yml). When that cap is full, nothing else spawns near them, even in the dark at night.

What fills it without you seeing it: huge dark caves under you full of zombies and skeletons, named mobs (with a name tag) or ones that picked something up from the ground, which never despawn, and animals in pens, which count towards the animal cap. That's why a mob farm that works up in the sky, far from the ground, stops working if there are unlit caves below.

If someone lowered spawn-limits in your bukkit.yml to reduce lag (for example monsters: 50), you'll also see fewer monsters. It's a trade-off: fewer mobs, less work for the server.

Check it with Paper's commands

Paper comes with commands that tell you how many mobs there are of each category and what the cap is. In the game, as an op, you type them with a slash; in the panel's “Console”, without a slash and giving the world or the player:

paper playermobcaps Name: that player's cap, category by category (monsters 70/70 means full). It's the one that matters with the per-player cap, which is the default.

paper mobcaps minecraft:overworld: the same for the whole world. With * instead of the world, all of them.

paper entity list minecraft:zombie minecraft:overworld: how many zombies there are and which chunks they pile up in (the 10 with the most). In the game, clicking a chunk takes you there. With * instead of minecraft:zombie, every mob.

paper playermobcaps Name
paper entity list minecraft:zombie minecraft:overworld

1. If it's full, light it up

   The extra mobs are usually in dark caves near the base or the farm: light them up, or clear them out. Lighting is what lasts.

2. Or remove the extra ones

   Very carefully and always with a type: kill @e[type=minecraft:zombie,distance=..128] removes the zombies within 128 blocks of whoever types it. Written without type, kill @e also wipes your animals, mounts and what's on the ground. First, a backup in “Backups”; the free server has no backups, so there it's better to light things up.

Plugins that remove or limit mobs

If none of the above explains it, look at the plugins. WorldGuard has the mob-spawning and deny-spawn flags: a region with mob-spawning deny (or the global region, __global__) lets nothing spawn. Lag-clearing plugins (ClearLag and similar) remove mobs every so often, and the ones that stack mobs or limit them per chunk change how farms work.

To be sure, take out the plugin you suspect for a moment: in “Files”, plugins folder, rename its .jar to .jar.off and press “Restart”. If the mobs come back, it was that one: check its config and give it its name back.

If you have several worlds with Multiverse, each one has its own game rules and difficulty: check all of the above in the world where they don't spawn (multiple worlds with Multiverse).

Frequently asked questions