Mob Spawner

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A player standing on top of a mob spawner.
When broken, spawners often leave visible flames floating where they were.
When spawners go very wrong...

"It's a flaming pig in a cage, why is it spitting out chickens?" ~Anonymous

A mob spawner is a block that intermittently produces either monsters or animals when the lighting and surrounding conditions are appropriate. They are naturally found in dungeons.

Obtaining spawners

Spawners can be found naturally occurring in dungeons or from hourly gifts.

Mob spawners in the MinecraftOnline server can be collected by hand, unlike in the vanilla server (where they don't drop an item when broken). Simply break them with a diamond pickaxe as usual.

Breaking spawners placed by other players counts as griefing, in the same way as any other player-placed block.

Alternatively, as with just about every other block, it can be purchased at shops if sellers stock it.

Setting up spawners

Once it has been placed, a spawner needs to be set to a specific monster type, using /setspawner <mob type>. A spawner type can also be changed at any time after placement with the same command.

Spawner types

Below is the chart for each available mobs.

Available Mobs for Spawners
Disposition Mobs Requirement * Overworld? Nether? End?
Passive Bat Light level 3 or less, and Y less than 63 O O
Passive Chicken Grass O O
Passive Cow Grass O O
Passive Mooshroom Mycelium (does not require Mushroom Fields biome) O O O
Passive Pig Grass O O O
Passive Sheep Grass O O
Neutral Spider Light level 7 or less O
Neutral Cave_Spider Light level 7 or less O
Hostile Creeper Light level 7 or less O
Hostile Husk Desert/Beach biome + moonlight O
Hostile Skeleton Light level 7 or less O O
Hostile Slime Y<40 (69 in swamp biome) O
Hostile Stray Snow/Ice biome + moonlight O
Hostile Zombie Light level 7 or less O
Hostile Magma Cube O
Hostile Wither_Skeleton Light level 11 or less O

* Requirement: Most mob spawning requirements are still required like usual, including distance from the mob spawner, light levels, etc. The above is just a brief description of those general spawning requirements.

Other mob types have been deemed too unfair to allow to be produced with spawners, as harvesting their drops would make certain challenging aspects of the game too easy.

Blaze spawners do exist, generated as usual in Nether Fortresses. However, you cannot use /setspawner blaze, so most players protect existing blaze spawners by placing blocks on all 6 sides, to prevent them from being changed to another mob type by someone using /setspawner. The same applies to Silverfish spawners, only generated inside Strongholds.

Farming/Grinder Usage

This section is user added by bcMineOut and is NOT official guidance.

This information is not sanctioned or approved by the Admin team and is generated from user based understanding of best practices as of May 2019 for MC v1.7.10. This guidance is to be considered subject to change and ultimately the Admin team will act on spawners as they feel necessary, even if it's contrary to this guidance.

While no formal rules have been codified on this topic, there appears to be some general best practices that should keep your spawner/grinder from being deactivated.

  • No Zombie grinders (Zombies are considered buggy and a cause for lag).
  • No more than 50 mobs present in a grinder while operator is AFK.
  • Avoid running grinders AFK in general.
  • No more that 10-15 spawners in a farm/grinder.
  • General feeling among users is 4-5 spawners should be a safe optimal number but YMMV.
  • Try to avoid running grinders when there is a high number of players on the server.

The key point here is that all grinders should be built to prevent massive build-ups of mobs and not be designed around the player sitting AFK at them. If your farm/grinder is a lag risk it is likely to be disabled. Another idea would be adding a manual on/off switch so your grinder is off when you're not around as an extra safeguard.

But, that being said, grinders appear to be evaluated on a case by case basis and action on them is wholly at the discretion of the Admin team based on situational and other concerns they may have.

Players are welcome to ask an Admin to evaluate their spawner setup for any obvious concerns with the understanding that those concerns could change at a later date.

Additional note: Several staff were approached to provide guidance on this topic at the time of writing and they deferred as they were wary of setting up player expectations/commitments and other concerns as expressed above.


  • It used to be necessary to ask admins to convert mob spawners they found in dungeons to an item, although this is no longer the case thanks to a drunken idea by SlowRiot.
  • Previously mob spawners had to be configured using the /mspawn command by a moderator - this was a risky business, as there were chances that a mistake could crash the server. This is no longer an issue since the creation of the /setspawner script.
  • Admins should take care not to confuse /setspawner with /setspawn - this is not the sort of mistake you want to make!
  • When broken, spawners often leave visible flames floating where they were. This can be fixed by relogging.
  • Spawners placed on grass produced invincible pigs before the 1.7 update, which were in fact client-side. Only you could see them, although most clients would produce their own invincible pigs when looking at the spawner, usually in different locations. They could be affected by you, and could move you around. It was one of Notch's little bugs caused by his deeply flawed philosophy of forking client code to make a server.
  • Zombie Pigmen (PigZombies) used to be permitted, as they dropped nothing. Now however they drop gold nuggets, making them a valuable resource.
  • Steves used to be able to be spawned, but Notch wrote them out of the game entirely. Villagers just aren't the same at all.

Further reading

See also