Tutorials/Mob farm

Mob farms are structures built to acquire mob drops more easily and in larger numbers. They usually consist of two components: a large, dark room to spawn mobs which are funneled into a central location, and a mob grinder to kill them quickly and efficiently.

Locations
The purpose for the farm is to provide a large area that is a viable spawn position for the intended targets, and to kill the mobs quickly. Due to the rules Minecraft applies to spawning mobs, this makes the choice of a location for the mob farm a difficult problem.

Farms placed on the surface can provide good drop rates during the day, when it is one of the few spots of dark ground, but has a sharp drop in effectiveness during nighttime, when the entire surface is dark enough to support mob spawning.

Farms built underground have a time-independent drop rate, and will remain within your personal spawn range for hostiles when you go mining, but their effectiveness depends on the amount of unlit caverns in your vicinity, which provide alternative places for mobs to spawn.

Farms floating high in the sky can achieve the best spawn rates during the day and night and you are far away from caves, as they represent the only viable spawn ground. However, building one in survival is rather dangerous, and due to their height they will stop working completely when you descend underground to mine resources. To produce loot, you have to stay at the height of the farm.

Farms constructed under an ocean can provide the best during day and night, as the ocean limits the viable spawn locations to open areas underground except for drowned which will spawn within the ocean water. You can also locate your base below it to ensure you will always be close enough to spawn monsters.

Superflat worlds will provide higher spawn rates than other worlds, as the missing air pockets underground reduce the amount of dark places.

The Nether is difficult to farm, as water evaporates and most mobs are immune to fire. This reduces the amount of functioning farm designs considerably. One could try to funnel the mobs through Nether Portals to circumvent the restrictions.

Drops
What a mob farm produces depends on location and the type of grinder used to kill the mobs. Automatic killing prevents certain drops and experience, but is safer as the player is not required to be near the mobs. The following is a table of mobs that can be effectively farmed and their usual and player-caused drops. Player-caused drops and experience can be obtained only when the monster is killed directly by the player or a tamed wolf.

Note that zombie, skeleton, and creeper heads will only drop if killed by a charged creeper. Wither skeletons, however, have a small chance to drop theirs no matter the cause of death, but still will always drop them when killed via charged creeper.

Designs
When planning a mob farm, one should consider the size of the spawnable area. The maximum spawnable area depends on where one plans to be in relation to the farm. If you plan to be directly beneath the center of the farm, waiting for the items, then the radius in which mobs can spawn can be used to calculate the maximum size of the spawnable area: floor( sqrt(Spawn Radius^2 - (Spawn Floor Height - Collection Floor Height)^2 )) = Spawnable Area $$ the spawn radius is 128 blocks. $$ the spawn radius is roughly 96 blocks for simulation distances > 4. For simulation distance 4 $$ the spawn radius is 44 blocks.

In practice, however, it is rarely worthwhile to fill the maximum spawnable area with a single farm that delivers mobs to central location. For example, if you plan to spend your time in a less defined position, it might be easier to repeat a simple design several times, ensuring that at least some areas are in the spawn range while limiting complexity. Moreover, transporting mobs long distances for killing will make a farm less efficient because of caps that limit spawning based on the number of mobs already in the loaded areas around the player. The impact of caps is especially important $$, which has caps that limit population densities as well as a global cap that counts mobs around every player loaded in the world.

TIP: If you are making a room that relies on darkness to spawn mobs, cave sounds and bats are good signs that your spawner is dark enough to let hostile mobs spawn.

Spawning Tower
One of the most popular overworld designs for a general mob farm is based on a tower of spawning pads that are periodically flushed with water to push the mobs off so that they die from fall damage. The water comes from a central pillar of dispensers and observers that cascade a clock signal between platforms. This type of farm is known for its high production rates, simplicity, reliability, and ease of build. Examples are provided in the videos below for Java and work in 1.16.

Using observer blocks
The designs shown in the YouTube videos above are somewhat resource intensive, but this design requires only the following materials:
 * 1 dispenser (per layer)
 * 1 water bucket (per layer)
 * 1 observer (per layer)
 * 112 opaque blocks of choice (per layer)
 * 1 clock (e.g. an Ethonian hopper clock: 2 hoppers, 2 sticky pistons, 2 comparators)
 * A capture layer (just several dozen hoppers leading into a chest)

In addition to being inexpensive, it is also easier to build.

The design uses three different layers that are repeated with a redstone clock added to the top layer. The layers are as follows:


 * 1) Top layer: An observer block, facing up observing the dispenser it; the rest of this layer is air.
 * 2) Middle layer: This layer is completely air (once the dispenser is triggered, it will be filled with water taking the block above the dispenser at it's center).
 * 3) Bottom layer: The dispenser (facing up, surrounded by opaque blocks (e.g. cobblestone) to hold the water. Fill the dispensers are filled with a bucket of water.

For layer one, the blocks must hold all of the water, so go out seven blocks in each direction, then fill in diagonally. Optionally, you can surround these blocks with signs to prevent spiders from climbing up. However, this would be a large amount of work for little benefit.

This mechanism can cascade downwards through quasi-connectivity. When the top dispenser is triggered the observer see the state change and signals down to the air gap above the dispenser below, activating it through quasi-connectivity.

This will cascade down through all of the layers (make as many as you like, but anywhere between 3 and 10 should be plenty). To start this cascade, the topmost dispenser needs to be activated. It is recommended to do so using an Ethonian hopper clock with about ten items in it. You can trigger the topmost observer using the redstone output from one of the emplacement the redstone block could be in the clock. It is also recommended to make the layer on which you place the clock bigger than the other the hide the layers under from the sun, and to place torchs on it to prevent mob spawn.

Sinkhole
The easiest possible design consists of a large, empty area of simple shape, with one or more holes in the ground for the mobs to drop through. The edge of each hole has to be lined with opened trapdoors or gates to trick the Mob AI into believing the hole to be solid ground. Trapdoors can also be controlled with redstone, so one could shut off the farm by closing the holes remotely.

The whole room is closed by a roof to create a minimal light level. A roof height of 3 allows Endermen to spawn, while a roof height of 1 would restrict the farm to spiders.

Sinkhole farms are not very effective, as the chance for a mob to wander into a hole is small, and zero when the player is so far away that the mobs freeze. But they can be built quickly and cheaply and will work in the Nether as well (which other designs requiring water won't, because you can't place water in the Nether).

Canal-style
To improve the chances of a mob falling into the holes, one can add channels filled with flowing water, leading to the central hole. The channels are lined with open trapdoors to trick the mobs into falling in, and the water transports them into the grinders. Such a design requires a bit of planning to ensure that there is no stationary water in which the mobs might get stuck, reducing effectiveness.

Since the system uses water to transport mobs, it will fail to capture Endermen, which teleport away when touching water. Therefore, the roof of the cavern should be 2 blocks above the ground to prevent griefing of your farm by Endermen taking blocks.

Compact canal design
A very easily built design can be made in a 20x20 area, using eight water source blocks to fill the channels, which are exactly eight blocks long so that the water stops exactly at the edges of the central hole. The design can be easily stacked or placed next to each other to increase the effectiveness. This design can be made even smaller as shown in the video (14x14 area). Shrinking the design can be done by using signs to cut off the water flow at the edge of the sinkhole, forcing the mobs to fall into the central hole.

Minimal canal design
If there is not enough space for larger designs, this might be used. Its small size of 10x10 or 20x20 (inner area) makes it able to be incorporated into larger construction projects without trouble. It uses four water source blocks, one in each corner, with the water flowing around 3x3 squares of building material to the central hole. The parts of the water between the wall and the blocks is closed over to provide more spawning area.

Large Chamber Fully Automatic Design
This is a very large farm that requires a lot of resources, it has 6 spawn chambers in each building, and redstone controlling it. It outputs 4 waves of average 10-15 mobs every 16 or so seconds.

Active mob displacement
The Canal-Style System still suffers from the mobs freezing when outside a certain range around your character $$, and from the limitations of low population density caps $$. Active Systems can correct that problem. One example is using Redstone and Dispensers filled with a Water bucket to flood the spawning grounds repeatedly, flushing all mobs into the channels to be transported to the grinders. Thus, the farm provides area for the mobs to spawn in, but does not rely on mob movement to get them into the grinder. Using this, one can omit the trapdoors needed for the other, passive designs.

$$ placing water on top of scaffolding provides a very efficient means of active transport. Land mobs spawn with their feet inside of the scaffolding and their heads inside of the flowing water. The mobs are then immediately transported to a drop chute or other killing area. Spiders and baby mobs present a challenge for water-on-scaffolding designs because they spawn entirely inside of the scaffolding and will not be moved by the water until they randomly climb/jump. Several methods have been invented to deal with this: buttons placed every-other block in every-other row will block spiders from spawning at all; villagers can be used to lure baby zombies (see below); snow golems can be used to knock mobs upward and into the flowing water; or cascading water down a funnel-shaped spawn floor can be used to pull babies and spiders into the water flow at every block. The farm below uses the funnel shape to produce a very high output.

Other designs
Instead of using water to transport mobs, there are various other methods to make them move towards the grinder, all of which may work better with certain mobs, but can have higher resource requirements or lesser gathering rates.

Sunlight mob farm
The sunlight mob farm utilizes the fact that undead mobs seek protection from sunlight. Using an roof three blocks off of the ground as the lure, open trap doors can be used to trick the mobs into falling into a grinder. The only downside of the farm is that it attracts only zombies and skeletons.

Villager
This method works only on zombies and drowned because they are attracted to villagers. This is tricky, as you need a village to get the villager into the right position. This method works by having one or more villagers trapped in a place, so they can't get out. Any nearby zombies will go to the villagers. You can make a maze that the zombies have to go through so that you need only one trap. However, there needs to be some sort of trap that the zombies will fall in to get to the villagers (e.g. a ton of soul sand in water or in air, fall damage, etc.).

Turtle Eggs
This method only works on zombies, drowned and zombified piglins. This method uses turtle eggs, which have the unique property of attracting zombies and their variants. Turtle eggs can be used in combination with open trapdoors above a drop to lure any zombie-variant mobs into a killing chamber. It is a popular choice for zombified piglin farms in the nether and can be used as a method to lure zombies rather than other mobs in a standard mob farm.

One-way doors
Relying on the random movement of mobs, One-Way Door Designs use doors or pistons to prevent the mobs from wandering backwards. Making several sets of doors can increase the speed with which the mobs move towards the hole.

The easiest configuration consists of a wall of doors (Iron on Hard difficulty to prevent Zombies from smashing them, or fencegates, or maybe trapdoors somehow. Use wooden doors on other difficulties) with a row of pressure plates in front of them. When the mobs walk onto the pressure plates, the door opens, letting them through, but once on the other side, they can't open the door since there is no switch.

With Pistons, the arrangement is reversed, with the pressure plates on the desired side, and the pistons pointing upwards, so that they block the path of the mobs when extended. This design works only with a 2-block high roof to prevent the mobs from jumping, and even then might fail on spiders. However, it requires considerably more common ingredients than the iron door variant.

Such systems can also be used to "store" mobs after gathering them from the farm, so that they later can be killed for the rare drops and experience.

Slime
This farm design uses large slimes to push mobs off ledges. The simplest way to get these slimes are through a slime farm. As for the rates, it gets over 20,000 items per hour, as said in the video title.

Transporting mobs
After collecting the mobs from the farm, it might be beneficial to transport them to a different location before grinding them, so that you can access the items more easily while remaining at a close-to optimal position for the spawning of your farms.

Horizontal transportation
Horizontal Transportation can be done easily using flowing water, with a drop of 1 block vertically for every 8 block traveled horizontally. Build a tunnel with a height of 3 blocks and a width equal to the size of your gathering holes (usually 2). Mine forward to a length of 8 Blocks, so that water placed at the start ends exactly at the drop. Repeat, but one block lower, so that the mobs fall from one funnel part to the next. Mine out the roof at the higher level for 2 or 3 more blocks to prevent spider clinging to the walls from clogging up the funnel.

Alternatively, one can use a cactus to grind the spiders immediately. To do this, make the first funnel part only 7 block long and place only one water source block instead of two. Place a sand block and a cactus on top on the same side as the source block. To place the cactus, you have to mine out the block next to it. To ensure the water flow on the next part, mine out the wall block next to the sand and add the water sources there and next to the sand, where there would usually be one.

Downward transportation
Transporting mobs and items downward is trivial, simply let them drop down a chute with a water brake at the bottom. Or omit the water brake when you want the mobs to die from fall damage.

Upward transportation
Upward transportation uses the fact that nearly all mobs will attempt to swim in water, moving upwards. Therefore, to get the mobs moving upwards, one has to provide only a column of water with enough air holes to prevent them from drowning. This can be done by arranging signs or ladders and water source blocks in the following vertical configuration:

This can be repeated indefinitely in any direction for a mob elevator. When arriving at the right height, flowing water on top of the topmost ladder is enough to dislodge them.

Slimes will not swim in versions prior to Java Edition 1.8, which can be used to separate them from other mobs.

As of Java Edition 1.13 and Bedrock Edition 1.5.0, a block of soul sand can be placed at the bottom of a column of water source blocks to force entities quickly upwards, while also supplying air for long distances. If soul sand is not used, undead mobs can be separated from the others because they will not swim upwards.

Grinding
The last part of a mob farm is to kill the gathered mobs and collect their items. This can be done in different ways, using the variety of damage available in Minecraft, like falling, suffocating, drowning, burning, sunlight (for undead), touching cacti, simply player-applied damage from weapons or lava.

Passive Systems do not change to kill the mobs, they rely on constantly available damage sources. Traditional mob grinders used "Lava Blades" and "Drowning Traps" while newer models use magma blocks to kill mobs above the minecart/hopper retrieval system.

Active Systems have to change configuration to actually kill mobs, usually in the form of redstone devices. The most known might be the "Piston Grinder", which applies suffocation damage by pushing an opaque block into the head of the mob. While possibly faster than passive systems in killing, active systems usually have a limited capacity, and higher amounts of mobs might clog or even jam the system. The "Minecart Grinder" uses Minecarts to carry the mobs into one block high space, suffocating them. This method can jam up too, but is fairly amusing. You could also use lava at the above the hoppers so you get the loot before the loot burns automatically.

EXP farms are systems that capture and soften up the mobs, but rely on the player to deliver the killing blow, so that the rare drops and experience can be gathered. An example would be a nearly-lethal falling height which would reduce the majority of mobs to half a heart, easily killed even without a weapon. However, such systems are only as good as the player using them, and in constant danger of being destroyed by creepers if not built out of obsidian, or if the player is out of sight of the creeper, in which case it will not explode. Also on bedrock edition one can make a piston push a trident back and forth for AFK xp.

With the Hopper, it becomes easy to collect the dropped items, even without player interference. This makes fully automatic mob farms possible where the loot will be deposited in a chest for easy accessibility.

Performance concerns

 * You should clear out the entire chunk where the mob farm is by placing torches. The game has a limit on the number of hostile mobs based on the number of loaded chunks, so it's a good idea to make sure all of them spawn in the farm.
 * You may need a somewhat beefy computer to operate the farm, since mob AI can be very taxing on the server component of the game program. Check the TPS indication if you are on singleplayer, or ask about the server host for rules on multiplayer servers. The quicker mobs are killed, the less likely AI is going to be a problem.

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