Slime

A slime is a hostile, animate, green, gelatinous, hopping, and relatively rare mob in the shape of a cube that appear in various sizes. They are able to see the player through solid blocks. When killed, a slime will split into smaller slimes, except for the smallest slime which will drop slimeballs instead. Slimes are found only in the lowest 40 layers of the Overworld, and only in certain areas. On Xbox 360, slimes are found only below layer 16. Slimes can spawn in flatland world types because its world generation level is 3 blocks above bedrock.

Usage
Slimeballs, which tiny slimes drop, are a key ingredient in sticky pistons, and can also be combined with blaze powder to create magma cream that can be used as an ingredient in the brewing of potions.

Behavior


Slimes move by hopping. They will always hop toward the closest player within 16 blocks (spherical) distance, even if they can't see that player. If no player is in range, they will simply hop in a straight line in whatever direction they were last facing. When they first spawn, they are facing in a randomly chosen direction. Slimes cannot swim upward in water, unlike walking mobs.

Tiny slimes deal no direct damage to the player or other entities, but can push them, occasionally into lava or other hazards. The larger slimes cause damage on contact proportional to their size.

Slimes of different sizes are not different mobs. A slime's size can be anywhere from 1 to 256, though only sizes 1, 2, and 4 spawn naturally, and their damage and health are calculated accordingly: a slime's attack strength is equal to its size (With the exception of size 1), and its health is its size squared. When a slime is killed, it splits into 2-4 more slimes half its numeric size, rounded down. Tiny slimes will not split, but will drop 0-2 slimeballs.

Slimes can take damage in all the usual ways: burning, falling, drowning, suffocating inside blocks, being attacked, falling into The Void, etc. Slimes can trample farmland.

In shallow water, slimes can hop fast enough to fight the current, as long as their hopping is not obstructed by a low ceiling. They will sink in deep water and won't be able to hop while submerged. And if they stay submerged for too long, they will die. They can also climb ladders, and be pushed over slabs and stairs.

While big and small slimes make a wet slapping noise, tiny slimes create the same sound as a player would walk on the block they are hopping on. Larger slimes make a splattering sound distinct from their movement noises when damaging a player. Slimes do not grow larger or smaller over time. An interesting observation about slimes is that when you spawn at least five of them in the overworld, they all seem to hop in the same direction rather than wandering around aimlessly like a regular mob. This also applies for Magma Cubes.

Spawning
Slimes spawn only below layer 40 (16 on Xbox 360), and only in certain chunks that are determined pseudo-randomly by the seed of the world. Roughly 10% of chunks will be able to spawn slimes, based on the formula: Random rnd = new Random(seed +                         (long) (xPosition * xPosition * 0x4c1906) +                          (long) (xPosition * 0x5ac0db) +                          (long) (zPosition * zPosition) * 0x4307a7L +                          (long) (zPosition * 0x5f24f) ^ 0x3ad8025f); return rnd.nextInt(10) == 0;

That is, using the chunk coordinates to help generate a seed, a random number between 0 and 9 will be generated, and if that number is 0, the chunk will be able to spawn slimes. To convert world coordinates to chunk coordinates, divide by 16 and round down.

Tools exist to calculate which chunks are slime chunks—see Slime Finding Tools.

Due to the surface of flatland worlds being generated 3 blocks above bedrock (well below the necessary height level for slimes to spawn), slimes tend to spawn abundantly on flatland map types. This is because there are no caves, all spawnable area is lit during the day and slimes are the only hostile mob that can spawn in the light.

Like most other mobs, Slimes require two vertical non-opaque blocks (e.g., air, signs, torches) to spawn in, with an opaque block underneath. The space they spawn in must also be clear of solid obstructions and liquids. Big Slimes require a 3x3x3 space to spawn, small Slimes require a 3x3x2 space, and tiny Slimes require a 1x1x2 space (or 1x1x1 if the upper block is not opaque). Slimes are equally likely to spawn at all sizes. Slimes are much more likely to spawn in a 3 high room.

Slimes spawn only 1/10th as often as other hostile mobs, so they can be hard to find. Slimes can spawn in any light level and lighting does not affect their spawn rate. However, lighting up the surrounding area does decrease the chances of non-slime mobs spawning and thus indirectly increases slime spawning rates. But remember not to place glowstone on the floor. Ever since Beta 1.6.6, glowstone has the property of glass so mobs cannot spawn on it. When lighting the floor, Jack-o-lanterns are recommended. Slimes have equal chances to spawn at any size. It is intended for tiny slimes spawn in peaceful mode, however, the code to allow this is skipped over when the game is on peaceful, and instantly despawns them just like any other hostile mob.

Like any hostile mob, slimes will not spawn within 24 meters (spherical) of any player. Similarly, slimes will despawn after some time if no player is within 32 meters, and despawn instantly if no player is within 128 meters.

The slime spawning algorithm is discussed in greater detail in this forum topic, but note that the algorithm has changed many times and older information may no longer be accurate.

Slime spawning (due to its unique spawning style) can interfere with other mob spawning.

Farming
Once a slime spawning chunk has been determined the process of encouraging slime spawning is relatively simple. The player can proceed in clearing out large rooms - typically 3 x 3 x 3 or larger - and should light them as to prevent the spawning of additional unwanted mobs. Waiting for slimes to spawn in these rooms can be lengthy at times, however. See the Slime spawning page on minecraftforum.net mentioned above for more information on how to increase this rate.

A similar method can also be used to players intending to play the game legitimately and avoid resorting to tools and mods. The player can simply descend below the maximum height allowed for slime spawning and strip mine a cavern. Approximately 10% of chunks will spawn slimes, so the cavern must be fairly large to have a good chance of finding one. A cavern that spans 7 chunks has a 50% chance of including one that produces slimes; 22 chunks must be excavated to reach a 90% chance. This method is not recommended but does work.

Finding a large Lava lake close to Bedrock can be extremely useful, as it will not only save the player a lot of digging, but can also provide enough natural light to prevent other mobs from spawning, and it can be made into a slime farm with as little effort as cooling the Lava with Water while leaving some for lighting.

Once slimes are found there are many ways to kill them. For smaller slimes the simple but effective, attack them with a sword, approach is found best but when up against larger slimes to use flint and steel to light the blocks between you and them, they will then move towards you and set themselves ablaze and break into more slimes.

Setting slimes on fire has become a popular method of getting slimeballs because the chances of the slimeballs burning is surprisingly low so through the use of netherrack setting parts of rooms where slimes spawn on fire is a great way to farm slimeballs.

A much easier alternative to the above is to dig out a pit large enough to hold all sizes of Slimes and fill it to the brim with water. Slimes cannot rise in water or hop around so they eventually drown, leaving Slimeballs when they perish.

The tutorials section provides some advice on managing slimes in superflat mode. Due to Slimes spawning in very large numbers on flatland maps, so there is no need to farm them, but they do need to be brought under control.

Slime Finding Tools


These tools can be used to find chunks that are eligible to spawn slimes:

http://mcslimes.appspot.com/ (Java applet, allows you to upload a level.dat file from a server or multiplayer for seed, very useful)

http://extension.ws/minecraft/slimes.html (HTML/JavaScript)

Rei's Minimap is also able to show this kind of chunks by highlighting them

What's My Light Level can also aid players in finding Slimes.

Minecraft X-Ray, since version 3.4.0 (external map-viewer, not a mod)

AMIDST Finds Slime chunks as well as Strongholds, Villages, and Biomes. (external program)

History
Slimes were the fifth hostile mob added to the game on July 23, 2010 (Seecret Friday 6! Alpha 1.0.11). When slimes were first added, there were four sizes: Tiny, Small, Big and Huge. Notch limited slime spawning shortly afterwards because they would appear in abundance. A miscalculation in the new limit caused slimes to only spawn in strange locations, so Notch then disabled natural slime spawning.

Small slimes started to drop 0 - 2 slimeballs in Beta. Notch confirmed in Coestar's livestream that slimes had been reskinned and returned in Beta 1.2_01 but were still very rare. Slimes became more common in Beta 1.3. A bug remedied in Beta 1.5 caused slimes to spawn in Peaceful mode and attack without any provocation. An SMP bug fixed in Beta 1.4 caused slimes that split to be visible only to the player that caused them to split and would not take any damage. Because these slimes were client-side, the player could only remove them by exiting and logging back into the server.

Since 1.9 prerelease, slimes always split upon death even if they take overkill damage. Before Beta 1.9 Pre-release 5, Slimes only appeared in the bottom 16 layers of the map regardless of light levels or time of day, often in large caverns or open mines.

In the Snapshot 12w38a Slime's Sounds were changed to a more liquid-esque sound

Bugs

 * Slimes are notorious for causing severe localized lag in multiplayer when they split into several smaller entities.
 * Slimes in SMP sometimes display as the wrong size, so it is often the case that you take damage from what looks like a harmless tiny slime.
 * Slimes in SMP often animate strangely, jittering up and down, and in some servers, disappear altogether sometimes(but can still be attacked and attack), though this is not always the case.
 * Slimes can go through glass.
 * If a slime is killed, and the user logs out before it despawns, upon returning its health will reset, and the slime be red and sideways, as if it's about to despawn, but resume hopping at the player.
 * Slimes will take fall damage. This will cause the bone-cracking impact sound when landing, which seems incorrect, as they have no bones and they are gelatinous.
 * Additionally, their nether counterpart, the magma cube takes no fall damage.
 * A very rare glitch where if you push a slime into the void right before it hops, it will come out of the void, as if it bounced on an air block.
 * Slimes in SMP can sometimes push players despite intervening blocks
 * In the Xbox 360 Edition, killing a slime with a sword will cause it not to split.

Trivia

 * Third party software can be used to create arbitrarily large slimes.
 * Slimes may have been inspired by a number of classic gaming monsters. Their shape and size resemble that of Gelatinous Cubes from Dungeons & Dragons (though admittedly that   probably comes more from Minecraft's cubic art design than as a direct homage), and their splitting behavior resembles that of Zols from The Legend of Zelda, Puddings from Nethack and Ameboids from Ratchet and Clank. The name and the large, cartoonish face may be a homage to Yuji Horii's iconic Slimes from the Dragon Quest series.
 * Slimes will only attack the player, even if a skeleton accidentally shoots it.
 * Slimes do not use the updated Mob AI, and still move directly towards its target, even if they will fall off a cliff.
 * There's a line in the code that's meant to allow tiny slimes to spawn on Peaceful, but the natural spawning algorithm skips hostile spawning entirely on Peaceful. As a result, this line won't even be reached. However, there are illegitimate ways to spawn tiny slimes on Peaceful, e.g. with a Slime Monster Spawner.
 * Magma Cubes, added in Beta 1.9, could be seen as the Nether equivalent of Slimes.
 * Slimes hop faster when pursuing a player.
 * Despite Slimes being hostile mobs, many players have tiny Slimes as pets since they follow and can't directly damage players. They will also push Minecarts you are in, allowing for Slime-powered minecarts as they follow you.
 * Jeb suggested that Slimes would spawn on the surface in jungles in 1.2, but this was never implemented.
 * From one large slime, the minimum experience you can get from killing it and all the slimes that split from it is 12, 4 from the largest, 2 from the 2 it splits into, and 1 from the 2 each of those split into. The maximum experience possible is if the big slime splits into 4 and each of those medium slimes split into 4, resulting is 28 total experience.
 * Slimes can climb ladders, but only do so accidentally.
 * Slimes drown if the water is higher than them because they sink in water.
 * Slimes do not prevent you from sleeping, meaning you do not get this message: You may not rest now, there are monsters nearby
 * As of Snapshot 12w25a Slime spawning in Superflat world type has reduced.
 * One-block ceilings of opaque blocks immediately below slimes will have a green "leak" particle effect (as with lava and water).