Slime

A slime is a hostile mob in the shape of a green cube in various sizes. They are able to see the player through solid blocks, and will always try to move directly toward players without regard for obstacles or hazards. When killed, a slime will split into smaller slimes. When killed, slimes will drop slimeballs.

Behavior
In Minecraft, only sizes 1, 2, and 4 spawn naturally, and with equal probability. With use of, slimes can potentially range from size 1 to 256.

Slimes move by hopping, which they will do each 10 to 30 ticks ($1⁄2$ to $1 1⁄2$ seconds). Their exact routine is as follows:

The Slime will search for a player within 16 blocks (spherical) distance.
 * If no players are found, they wait 10 to 30 ticks ($1/2$ to $1 1/2$ seconds). Then they will change direction, by a random amount up to 57.26° (1 radian) left or right, jump, and repeat the process.
 * If a player is found, the delay before jumping will be $1⁄3$ as long (3 to 10 ticks), and the Slime's direction will be set directly toward the nearest player before jumping.

Combat
A slime's health is equal to their size squared, and its dimensions are 0.6 blocks times its size in each dimension. When a slime attacks, it will deal damage equal to its size, except for size 1 (smallest) slimes, which cannot do damage.

When the player kills a slime and the slime's size is larger than 1, it will die and spawn 2-4 new slimes equivalent to its size divided by 2, rounding down.

Drops
If the slime's size is 1, it will drop 0-2 slimeballs. If it is larger, it will only drop experience. All slimes drop experience equal to their size.

Spawning
Slimes spawn in areas below layer 40, and also spawn on the surface of swamps during the night, depending on the phase of the moon. In Superflat type worlds, the spawn rate is decreased.

Swamps
In swamps, slimes may spawn at night between the heights of 50 and 70 provided the light level is 8 or less. They spawn most often on a full moon, and never on a new moon. This can make gathering slimeballs difficult, as it takes over two hours for the moon to completely cycle.

More precisely, the game checks if the light level is equal to or less than a random integer (from 0 to 8), then if the fraction of the moon which is bright is greater than a random number (from 0 to 1). If these conditions are met and the altitude is acceptable, there is a 50% chance of spawning a slime.

Low layers
Slimes spawn throughout the world (except in mushroom islandss) below layer 40, but only in certain chunks, 1 in 10 of all chunks. However, in these chunks and layers, they spawn regardless of light level. The "slime chunks" are determined pseudo-randomly by combining their chunk coordinates with the seed of the world. Tools exist to calculate which chunks are slime chunks—see Slime Finding Tools.

One in 10 of chunks will be able to spawn slimes underground, 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.

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 unless a swamp biome is nearby, they can be hard to find. Slimes in low levels 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. Glowstone has the same properties as glass, so mobs cannot spawn on it.

Like other hostile mobs, slimes will not spawn within 24 meters (spherical) of any player, and will despawn instantly if no player is within 128 meters. However, other mobs will also randomly despawn over time if no player is within a 32 meter range. In contrast, slimes will never despawn if there are players within the 128 meter range.

Farming


Once a slime spawning chunk has been determined the process of encouraging slime spawning is relatively simple. The player can clear out large rooms - typically 3 x 3 x 3 or larger. It might be wise to light these rooms to prevent other hostile mobs from spawning. 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. Killing the slimes with either fire or water is recommended.

Pre-1.4 spawning
The (pre-1.4) 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.

Due to the relative difficulty of finding slimes before 1.4, a number of tools exist to aid the player in finding a location that can spawn slimes.

Slime finding tools



 * 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 able to highlight chunks with the ability to spawn slimes in a singleplayer game.
 * 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)

Trivia

 * Slime are dumb
 * Iron Golems and Dogs sometimes don´t kill Slimes
 * When a player receives damage from a slime, the "punching" sound effect that plays when taking damage sounds squishier and wetter than normal.
 * 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 comes more from Minecraft's cubic art design), while their splitting behavior resembles that of Zols and Chuchus from The Legend of Zelda, Puddings from Nethack and Amoeboids 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.
 * Since there's a limit on the number of hostile mobs that can exist in all the loaded chunks at once, splitting several slimes into tiny slimes and letting them follow you will greatly reduce the chances of encountering other monsters.
 * 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.
 * Slimes hop much 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.
 * 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 in 28 total experience.
 * Slimes can climb ladders, and once in pursuit of the player, their straight-line pursuit can take them right to the top, if a player is waiting there.
 * Slimes do not prevent you from sleeping, meaning you do not get this message: "You may not rest now, there are monsters nearby".
 * One-block ceilings of opaque blocks immediately below slimes will have a green "leak" particle effect (as with lava and water).
 * Because slimes spawn in swamps at night, they often jump in the water and kill themselves.
 * If you get inside a slime you'll see the old black eyes.
 * In old alpha, the third-person view wasn't centered, so that was an easy way to find slimes.
 * If you sprint-fly into a slime, you see their old texture.
 * As of the 1.6 pre-release, slimes have naturally been found in other biomes, especially in snow biomes, although this might be a rare occurrence.
 * To calculate the health of a slime, the formula is the following: size^2, so a slime with size 127 has a total of 16129 health points (8064.5 hearts); the same applies to magma cube.
 * Tiny slimes have the least amount of health of any mob in the game with only.