World generation

World generation (sometimes abbreviated as worldgen) is the procedural generation process Minecraft uses to algorithmically generate terrain, biomes, features, and thus ultimately decides which blocks are placed where. Minecraft worlds are made of 16×16 blocks wide chunks stretching the full height of the dimension. Because there are more than 18 quintillion (${\displaystyle 18\times 10^{18}}$) possible worlds, the game generates them using randomness, algorithms, and some manually built decorations. The benefits of procedural world generation include smaller game file size and practically infinite possibilities of gameplay.

Randomness

In order to generate a different world every time, the game uses random numbers generated from a seed. However, pure randomness makes terrain and biomes too chaotic with no continuity.^[1]

To solve this problem, the game makes use of gradient noise algorithms, like Perlin noise.^[2] This makes sure blocks and chunks fit with its neighbors and gives the world both continuity and randomness.

Even though noise looks random and continuous, using it to generate terrain still lacks variation like hills and valleys that stand out and have a large height difference. To solve this, multiple noise functions are generated with different frequencies and amplitudes and then added up, which gives a more natural result. These noise functions are called octaves.

• 
  Pure randomness (also known as white noise) is too chaotic.
• 
  Perlin noise makes it random and continuous.
• 
  Multiple octaves are combined to create variation.

Steps

World generation happens in multiple steps. The game may freeze some chunks that are far from players at an early generation step for better performance, as shown on the graph. As the player approaches these chunks, the chunks advance through the generation steps again until they finish generating. Incomplete chunks that are temporarily frozen at a step are called proto-chunks, while chunks that are ready and accessible to players are called level chunks. In Java Edition, the steps of world generation are sorted into:

• 
   empty: The chunk is not yet loaded or generated.
• 
   structures_starts: This step calculates the starting points for structure pieces. For structures that are the starting in this chunk, the position of all pieces are generated and stored.
• 
   structures_references: A reference to nearby chunks that have a structures' starting point are stored.
• 
   biomes: Biomes are determined and stored. No terrain is generated at this stage.
• 
   noise: The base terrain shape and liquid bodies are placed.
• 
   surface: The surface of the terrain is replaced with biome-dependent blocks.
• 
   carvers: Carvers carve certain parts of the terrain and replace solid blocks with air.
• 
   features: Features and structure pieces are placed and heightmaps are generated.
• 
   initialize_light: The lighting engine is initialized and light sources are identified.
• 
   light: The lighting engine calculates the light level for blocks.
• 
   spawn: Mobs are spawned.
• 
   full: Generation is done and a chunk can now be loaded. The proto-chunk is now converted to a level chunk and all block updates deferred in the above steps are executed.

Biomes

Overworld

Biome generation in the Overworld is based on 6 parameters: temperature, humidity (aka. vegetation), continentalness (aka. continents), erosion, weirdness (aka. ridges), and depth. Except for "depth", the other 5 parameters are based only on horizontal coordinates.

They can be thought of as a six-dimensional (6D) space, where multiple intervals are defined for each biome, as described below. If the 6 parameters at a location fall outside all the defined biome intervals, the game uses the closest biome interval in the 6D space.

Temperature is a noise parameter used only in biome generation and does not affect terrain generation. Temperature values are divided into 5 levels. The corresponding ranges from level 0 to level 4 are: -1.0~-0.45, -0.45~-0.15, -0.15~0.2, 0.2~0.55, 0.55~1.0.

Note that the temperature parameter is not the same as the temperature property of a biome, but they roughly correspond each other, e.g. if a location's temperature parameter is level 0, the base temperature of the biome here is usually low enough or the terrain is high enough, that the surface is covered in snow and ice.

Humidity (also known as vegetation) is a noise parameter used only in biome generation and does not affect terrain generation. Humidity values are also divided into 5 levels. The corresponding ranges from level 0 to level 4 are: -1.0~-0.35, -0.35~-0.1, -0.1~0.1, 0.1~0.3, 0.3~1.0.

Continentalness (also known as continents) is used to decide between ocean/beach/land biomes. Higher values correspond to more inland biomes.

• If -1.2~-1.05: Mushroom fields
• If -1.05~-0.455: Deep ocean
• If -0.455~-0.19: Ocean
• If -0.19~-0.11: Coast
• If -0.11~0.03: Near-inland
• If 0.03~0.3: Mid-inland
• If 0.3~1.0: Far-inland

Erosion is mainly used to decide between flat and mountainous biomes. When erosion is high the landscape is generally flat. Erosion values are divided into 7 levels. The corresponding ranges from level 0 to level 6 are: -1.0~-0.78, -0.78~-0.375, -0.375~-0.2225, -0.2225~0.05, 0.05~0.45, 0.45~0.55, 0.55~1.0.

Weirdness (also known as ridges) affects whether to generate a biome variant or not. If the weirdness value is greater than 0, the generated biome becomes weirder. For example, using the variant of the Jungle biome — Bamboo Jungle. Additionally, weirdness also affects where peaks and valleys generate. Because of this, a biome and its variant often do not appear on the same bank of a river.

The PV (peaks and valleys, aka. ridges folded) value is calculated through the formula ${\displaystyle 1-|(3|weirdness|)-2|}$.

• If -1.0~-0.85: Valleys
• If -0.85~-0.2: Low
• If -0.2~0.2: Mid
• If 0.2~0.7: High
• If 0.7~1.0: Peaks

Depth is a parameter not based directly on noise, instead it corresponds approximately to the terrain height. It is roughly 0 at the surface and increases by ¹⁄₁₂₈ (0.0078125) for every 1 block down. The depth parameter affects whether a surface biome or a cave biome is placed.

The table below lists the defined depth values for Overworld biomes, and any additional noise values required for cave biomes to generate. Any other values result in the closest biome interval being used instead. Note that regions of lush caves and dripstone caves overlap.^[3]

Depth	Additional requirement	Biomes
D=0.0	N/A	Surface biomes
D=0.2~0.9	Continentalness=0.8~1.0	Dripstone Caves
D=0.2~0.9	Humidity=0.7~1.0	Lush Caves
D=1.0	N/A	Surface biomes
D=1.1	Erosion=-1.0~-0.375	Deep Dark

The generation of non-inland biomes is not based on humidity, erosion and weirdness. The following table lists the relation between non-inland surface biomes and continentalness and temperature.

Temperature	Oceans	Deep oceans	Mushroom fields
T=0	Frozen Ocean	Deep Frozen Ocean	Mushroom Fields
T=1	Cold Ocean	Deep Cold Ocean
T=2	Ocean	Deep Ocean
T=3	Lukewarm Ocean	Deep Lukewarm Ocean
T=4	Warm Ocean

The following table lists the relation between inland surface biomes and continentalness, erosion and PV.

PV	Erosion	Coast	Near-inland	Mid-inland	Far-inland
Valleys	E=0~1	Frozen River（T=0） River（T>0)	Frozen River（T=0） River（T>0）	Middle biomes[bo 1]（T<4） Badland biomes[bo 1]（T=4）
	E=2~5			Frozen River（T=0） River（T>0）
	E=6		Frozen River（T=0） Swamp（T=1,2） Mangrove Swamp（T=3,4）
Low	E=0~1	Stony Shore	Middle biomes（T<4） Badland biomes（T=4）	Snowy Slopes（T=0; H=0,1） Grove（T=0; H=2,3,4） Middle biomes（0<T<4） Badland biomes（T=4）
	E=2		Middle biomes	Middle biomes（T<4） Badland biomes（T=4）
	E=3	Beach biomes
	E=4			Middle biomes
	E=5	Beach biomes（W<0） Middle biomes（W>0; T=0,1 OR H=4） Windswept Savanna（W>0; T=2,3,4; H=0,1,2,3）	Middle biomes（W<0 OR T=0,1 OR H=4） Windswept Savanna（W>0; T=2,3,4; H=0,1,2,3）
	E=6	Beach biomes	Middle biomes（T=0） Swamp（T=1,2） Mangrove Swamp（T=3,4）
Mid	E=0	Stony Shore	Snowy Slopes（T<3; H=0,1） Grove（T<3; H=2,3,4） Plateau biomes（T=3,4）
	E=1		Snowy Slopes（T=0; H=0,1） Grove（T=0; H=2,3,4） Middle biomes（0<T<4） Badland biomes（T=4）		Snowy Slopes（T=0; H=0,1） Grove（T=0; H=2,3,4） Plateau biomes（T>0）
	E=2		Middle biomes	Middle biomes（T<4） Badland biomes（T=4）	Plateau biomes
	E=3	Middle biomes			Middle biomes（T<4） Badland biomes（T=4）
	E=4	Beach biomes（W<0） Middle biomes（W>0）		Middle biomes
	E=5	Beach biomes（W<0） Middle biomes（W>0; T=0,1 OR H=4） Windswept Savanna（W>0; T=2,3,4; H=0,1,2,3）	Middle biomes（W<0 OR T=0,1 OR H=4） Windswept Savanna（W>0; T=2,3,4; H=0,1,2,3）	Shattered biomes
	E=6	Beach biomes（W<0） Middle biomes（W>0）	Middle biomes（T=0） Swamp（T=1,2） Mangrove Swamp（T=3,4）
High	E=0	Middle biomes	Snowy Slopes（T<3; H=0,1） Grove（T<3; H=2,3,4） Plateau biomes（T=3,4）	Jagged Peaks（T=0,1,2; W<0） Frozen Peaks（T=0,1,2; W>0） Stony Peaks（T=3） Badland biomes（T=4）
	E=1		Snowy Slopes（T=0; H=0,1） Grove（T=0; H=2,3,4） Middle biomes（0<T<4） Badland biomes（T=4）	Snowy Slopes（T<3; H=0,1） Grove（T<3; H=2,3,4） Plateau biomes（T=3,4）
	E=2		Middle biomes	Plateau biomes	Plateau biomes
	E=3			Middle biomes（T<4） Badland biomes（T=4）
	E=4			Middle biomes
	E=5	Middle biomes（W<0 OR T=0,1 OR H=4） Windswept Savanna（W>0; T=2,3,4; H=0,1,2,3）		Shattered biomes
	E=6	Middle biomes
Peaks	E=0	Jagged Peaks（T=0,1,2; W<0） Frozen Peaks（T=0,1,2; W>0） Stony Peaks（T=3） Badland biomes（T=4）		Jagged Peaks（T=0,1,2; W<0） Frozen Peaks（T=0,1,2; W>0） Stony Peaks（T=3） Badland biomes（T=4）
	E=1	Snowy Slopes（T=0; H=0,1） Grove（T=0; H=2,3,4） Middle biomes（0<T<4） Badland biomes（T=4）
	E=2	Middle biomes		Plateau biomes	Plateau biomes
	E=3			Middle biomes（T<4） Badland biomes（T=4）
	E=4			Middle biomes
	E=5	Shattered biomes（W<0 OR T=0,1 OR H=4） Windswept Savanna（W>0; T=2,3,4; H=0,1,2,3）		Shattered biomes
	E=6	Middle biomes

In which, the specific biome generation of beach biomes, badland biomes, middle biomes, plateau biomes, and shattered biomes is determined by the temperature, humidity, and weirdness values.

Beach biomes generate in low lying terrain along the coast, and the specific biome generation is related only to the temperature value.

Temperature	Biomes
T=0	Snowy Beach
T=1,2,3	Beach
T=4	Desert

Badland biomes usually generate inland with low erosion value, and can also generate along the coast with high terrain and low erosion. The specific biome generation is related to humidity and weirdness.

Humidity	Biomes
H=0,1	Badlands（W<0） Eroded Badlands（W>0）
H=2	Badlands
H=3,4	Wooded Badlands

Middle biomes are the most extensive biomes inland. The specific biome generation depends on temperature, humidity, and weirdness.

Temperature Humidity	T=0	T=1	T=2	T=3	T=4
H=0	Snowy Plains（W<0） Ice Spikes（W>0）	Plains	Flower Forest（W<0） Sunflower Plains（W>0）	Savanna	Desert
H=1	Snowy Plains		Plains
H=2	Snowy Plains（W<0） Snowy Taiga（W>0）	Forest		Forest（W<0） Plains（W>0）
H=3	Snowy Taiga	Taiga	Birch Forest（W<0） Old Growth Birch Forest（W>0）	Jungle（W<0） Sparse Jungle（W>0）
H=4	Taiga	Old Growth Spruce Taiga（W<0） Old Growth Pine Taiga（W>0）	Dark Forest	Jungle（W<0） Bamboo Jungle（W>0）

Plateau biomes generate at inland high terrain with moderate erosion, which results in biomes like meadows and savanna plateaus. The specific biome generation depends on temperature, humidity, and weirdness.

Temperature Humidity	T=0	T=1	T=2	T=3	T=4
H=0	Snowy Plains（W<0） Ice Spikes（W>0）	Meadow（W<0） Cherry Grove（W>0）	Meadow（W<0） Cherry Grove（W>0）	Savanna Plateau	Badlands（W<0） Eroded Badlands（W>0）
H=1	Snowy Plains	Meadow
H=2		Forest（W<0） Meadow（W>0）	Meadow（W<0） Forest（W>0）	Forest	Badlands
H=3	Snowy Taiga	Taiga（W<0） Meadow（W>0）	Meadow（W<0） Birch Forest（W>0）		Wooded Badlands
H=4		Old Growth Spruce Taiga（W<0） Old Growth Pine Taiga（W>0）	Pale Garden	Jungle

Shattered biomes are generated at inland places with high erosion. The specific biome generation depends on temperature, humidity, and weirdness.

Temperature Humidity	T=0~1	T=2	T=3	T=4
H=0~1	Windswept Gravelly Hills	Windswept Hills	Savanna	Desert
H=2	Windswept Hills		Forest（W<0） Plains（W>0）
H=3	Windswept Forest		Jungle（W<0） Sparse Jungle（W>0）
H=4			Jungle（W<0） Bamboo Jungle（W>0）

The Nether

The Nether uses 3 parameters to generate biomes: temperature, humidity and offset. Unlike the Overworld, the Nether specifies biomes with a single point.

The offset parameter is not a noise, instead it is always 0 at any location in a world. This means that the parameter point of a location is always in the temperature-humidity-plane. The closer the offset (of a biome point) is to 0, the closer the point is to the T-H-plane and the greater the advantage it has during biome generation.

Biomes	Temperature	Humidity	Offset
Basalt Deltas	-0.5	0	0.175
Crimson Forest	0.4	0	0
Nether Wastes	0	0	0
Soul Sand Valley	0	-0.5	0
Warped Forest	0	0.5	0.375

The End

In Java Edition, the End uses only one noise parameter: erosion. If the horizontal distance from the chunk origin of a chunk to the world origin is less than 1024, the blocks in the chunk are in The End. Otherwise, the biome is determined by erosion.

Biome	Erosion	Distance
Small End Islands	-1~-0.21875	>1024
End Barrens	-0.21875~-0.0625
End Midlands	-0.0625~0.25
End Highlands	0.25~1
The End	N/A	<1024

In Bedrock Edition, the End has only one biome: The End.

Terrain

Terrain shaping determines which blocks should be solid and which blocks should be filled with air.

3D noise

If the noise is in two dimensions, it controls only surface height and it is impossible to add terrain above the surface. To add overhangs and 3D shapes, the game uses 3D Perlin noise function that gives an output called density for every single block. A density > 0 means it is filled with solid block, otherwise it is filled with air.

Density is then given a height bias and a base height. Height bias "squeezes" the blocks. Base height is the base of the squeezing process where the density is left unchanged. Changing base height moves the ground up and down.

• In the Overworld, there is a single pair of height bias and base height, meaning the higher the block is, the less density it has and vice versa. Height bias and base height are both configured by a couple of different noises. Notably, amplified worlds are generated by tuning height bias to be lower than default, so that terrain stretch in the vertical direction more.
• In the Nether, there are two pairs of base heights that create the thick, solid ceiling and ground, and the hollow space between them.
• In the End, these parameters are configured to squeeze the map into a big island located relatively at the bottom of the dimension.

• 
  The side view of a world using a single noise
• 
  The side view of a world using 3D noise, creating overhangs

Splines

To give the world some dramatic terrain shapes like cliffs, fjords and plateaus, the game uses three 2D noise maps. These noises are mapped using splines to calculate the height offset and a vertical stretch factor. The same noises are also used in biome generation, which creates a soft link between biome and terrain. For example, a mountainous area generates mountainous biome and plains biomes are generally flatter.

The larger the continentalness, the higher the average terrain height. Continentalness is used mainly for differentiating ocean and land.

The erosion parameter affects inland terrain during terrain generation. Erosion is mainly used to create large area of flat ground. The higher the erosion at a location, the lower the terrain height and the flatter the terrain.

The peaks and valleys (PV) value is calculated from weirdness. As the name suggests, it is mainly used for generating better peaks and valleys. The higher the PV value, the higher the terrain. Usually, at places with low continentalness or high erosion, when the PV level is "Valleys", the terrain is low enough to generate rivers. At high terrain, negative weirdness values lead to taller and more jagged and point peaks. When the erosion level is approximately 5, positive weirdness values result in weird inland terrain that is shattered and extremely precipitous and craggy.

• 
  Continentalness creates distinction between land and ocean
• 
  Large area of flat plains is created by high erosion.
• 
  PV creates peaks and valleys like this fjord.

Noise caves

Noise caves are part of the base terrain generation and are generated using 3D Perlin noises. They come in the form of cheese caves, spaghetti caves, and noodle caves. Three noise maps, frequency, hollowness, and thickness, are parameters that control this process. Frequency controls the frequency of the cave generation.

• Cheese caves are pocket areas of the underground that come in various sizes. They are generated by taking the white area in a Perlin noise map. Hollowness controls the size of cheese caves.
• Spaghetti caves are long, narrow caves that wind their way through the underground. When generating, the edge of black and white part of noise image becomes air, making it look like long and wide spaghetti. Thickness controls the thickness of spaghetti caves.
• Noodle caves are a thinner and squigglier variant of spaghetti caves. They consist of tunnels usually 1 to 5 blocks in width. Its generating mechanism is similar to that of spaghetti caves. Thickness controls the thickness of noodle caves.

Additionally, noise pillars generate inside big cheese cave chambers. Frequency controls the frequency of the pillar generation while thickness control the thickness of them.

• 
  Inside of a cheese cave.
• 
  Inside of a spaghetti cave.
• 
  Inside of a noodle cave.

Aquifers

Aquifers are liquid systems used in the Overworld to determine the fluid in all empty areas. Without aquifers all empty areas between sea-level and y=-54 would be filled with water. Areas below y=-55 are always filled with lava. To avoid all caves being flooded, aquifers are used to determine the fluid state of each position instead. Aquifers don't change the lava below y=-55. An aquifer can be in 3 different states, with a state selected for each position:

• Empty: Always filled with air
• Flooded: As if aquifers didn't exist: filled with air above the sea-level and a fluid below.
• Local fluid level: Picks a local liquid level and fills areas below with a liquid and areas above with air.

For positions above the preliminary surface, the aquifer state is "Flooded". In areas of the deep dark (Erosion < -0.22 and Depth > 0.9) the state is always "Empty". Otherwise the state is determined bases on a noise. Values below 0.4 are "Empty", values above 0.8 are "Flooded", otherwise a local fluid level is used.

In positions near areas where the preliminary surface is below the sea-level the area of the "Flooded" aquifer state reaches slightly below the preliminary surface. In these areas the cutoff values for the noise are linearly decreased from 64 blocks below the preliminary surface upward. At the surface they are below -0.8 for "Empty" and above -0.3 for "Flooded". This causes the "Flooded" state to be much more common directly below rivers and oceans.

The local water level is determined in cells of size 16x40x16 blocks using a different noise. Whether to place water or lava is determined in cells of 64x40x64 blocks based on a third noise. Areas above y=-10 always use water.

Barriers are used to separate areas of different liquids and to separate liquids from air. The height of the barriers is dependent on a fourth noise, causing water or lava to sometimes spill over the barrier.

Ore veins

Ore veins generate only in the Overworld. Three noises are used for vein generation: toggle, ridge, and gap.

Toggle is always 0 outside Y=-60 to Y=51 and can be negative or positive inside the range. The game attempts to generate an iron or a copper vein depending on whether toggle is < 0 or > 0. The attempts might fail because veins have a configured generating height.

Ridge is always -0.08 if Y level is outside the range. If ridge is > 0, the game skips the block.

Gap determines the ratio of ore-to-filler material, between 10% and 30% for any given vein. For non-filler blocks, 98% generate as normal ore blocks, while 2% are generated as raw ore blocks (Block of Raw Copper and Block of Raw Iron, respectively).

The blocks used in vein generation are hardcoded, though their size can be changed with datapacks.

Surface

After the base terrain is generated, the game replaces some blocks with grass blocks, sand, dirt, etc., depending on the biome and other conditions.

Overworld

Conditions					Result block
Gradient Y=-64 → Y=-59					Bedrock
Surface[s 1]	Floor[s 2]	Wooded Badlands	Above Y=97	Noise[s 3]	Coarse Dirt
				No water above	Grass Block
				Otherwise	Dirt
		Swamp	At Y=63	Noise[s 4]	Water
		Mangrove Swamp	Between Y=61 and Y=63
	Badlands Eroded Badlands Wooded Badlands	Floor[s 2]	Above Y=256		Orange Terracotta
			Above Y=74	Noise[s 3]	Terracotta
				Otherwise	Hoodoo[s 5]
			Water no deeper than 1	Ceiling[s 6]	Red Sandstone
				Otherwise	Red Sand
			Erosion[s 7]		Orange Terracotta
			Water​		White Terracotta
			Ceiling[s 6]		Stone
			Otherwise		Gravel
		Surface is above Y=63	Above Y=63 and surface is below Y=74		Orange Terracotta
			Otherwise		Hoodoo[s 5]
		Floor[s 2]	Water no deeper than 6 blocks		White Terracotta
	Floor[s 2] and water no deeper than 1	Frozen Ocean Deep Frozen Ocean	Erosion[s 7]	No water above	Air
				Cold[s 8]	Ice
				Otherwise	Water
		Frozen Peaks	Steep face[s 9] or noise[s 10]		Packed Ice
			Ice noise within 0~0.025		Ice
			No water above		Snow Block
		Snowy Slopes	Steep face[s 9]		Stone
			Noise[s 11]	No water above	Powder Snow
			No water above		Snow Block
		Jagged Peaks	Steep face[s 9]		Stone
			No water above		Snow Block
		Grove	Noise[s 11]	No water above	Powder Snow
			No water above		Snow Block
		Stony Peaks	Calcite noise within -0.0125~0.0125		Calcite
			Otherwise		Stone
		Stony Shore	Noise[s 12]	Ceiling[s 6]	Stone
				Otherwise	Gravel
			Otherwise		Stone
		Windswept Hills	Surface noise ≥ 4/33		Stone
		Warm Ocean Beach Snowy Beach Desert	Ceiling[s 6]		Sandstone
			Otherwise		Sand
		Dripstone Caves			Stone
		Windswept Savanna	Surface noise ≥ 7/33		Stone
			Surface noise ≥ -2/33		Coarse Dirt
		Windswept Gravelly Hills	Surface noise ≥ 8/33	Ceiling	Stone
				Otherwise	Gravel
			Surface noise ≥ 4/33		Stone
			Surface noise ≥ -4/33	No water above	Grass Block
				Otherwise	Dirt
			Ceiling		Stone
			Otherwise		Gravel
		Old Growth Pine Taiga Old Growth Spruce Taiga	Surface noise ≥ 7/33		Coarse Dirt
			Surface noise ≥ 19/165		Podzol
		Ice Spikes	No water above		Snow Block
		Mangrove Swamp			Mud
		Mushroom Fields			Mycelium
		No water above			Grass Block
		Otherwise			Dirt
	Floor[s 2] and water no deeper than 6	Frozen Ocean Deep Frozen Ocean	Erosion[s 7]		Water
	Floor with depth[s 13] and water no deeper than 6	Frozen Peaks	Steep face[s 9] or noise[s 14]		Packed ice
			Ice noise within -0.0625~0.025		Ice
			No water above		Snow Block
		Snowy Slopes	Steep face[s 9]		Stone
			Noise[s 15]	No water above	Powder Snow
			No water above		Snow Block
		Jagged Peaks			Stone
		Grove	Noise[s 15]	Above water	Powder Snow
Otherwise			Dirt
Stony Peaks	Calcite noise within -0.0125~0.0125		Calcite
	Otherwise		Stone
Stony Shore	Noise[s 12]	Ceiling[s 6]	Stone
		Otherwise	Gravel
	Otherwise		Stone
Windswept Hills	Surface noise ≥ 4/33		Stone
Warm Ocean Beach Snowy Beach Desert	Ceiling[s 6]		Sandstone
	Otherwise		Sand
Dripstone Caves			Stone
Windswept Savanna	Surface noise ≥ 7/33		Stone
Windswept Gravelly Hills	Surface noise ≥ 8/33	Ceiling	Stone
		Otherwise	Gravel
	Surface noise ≥ 4/33		Stone
	Surface noise ≥ -4/33		Dirt
	Ceiling		Stone
	Otherwise		Gravel
Mangrove Swamp			Mud
Otherwise			Dirt
Warm Ocean Beach Snowy Beach	Floor with depth and secondary depth 6			Sandstone
Desert	Floor with depth and secondary depth 30
Floor[s 2]	Frozen Peaks Jagged Peaks			Stone
	Warm Ocean Lukewarm Ocean Deep Lukewarm Ocean	Ceiling		Sandstone
		Otherwise		Sand
	Ceiling			Stone
	Otherwise			Gravel
Below Y=0 and gradient Y=0 → Y=8					Deepslate
Otherwise					Stone

The Nether

Conditions					Result block
Gradient Y=0 → Y=5					Bedrock
Gradient Y=127 → Y=122
Above Y=122					Netherrack
Basalt Deltas	Ceiling[s 6]				Basalt
	Floor[s 2]	Patch noise ≥ -0.012	Surface between Y=30 and Y=35		Gravel
		Nether noise ≥ 0
	Otherwise				Blackstone
Soul Sand Valley	Ceiling[s 6]	Nether noise ≥ 0			Soul Sand
		Otherwise			Soul Soil
	Floor[s 2]	Patch noise ≥ -0.012	Surface between Y=30 and Y=35		Soul Sand
		Nether noise ≥ 0			Soul Sand
		Otherwise			Soul Soil
Floor[s 2]	Below Y=33	Erosion[s 7]			Lava
	Warped Forest	Netherack noise ≥ 0.54	Above Y=31	Nether wart noise ≥ 1.17	Warped Wart Block
				Otherwise	Warped Nylium
	Crimson Forest	Netherack noise ≥ 0.54	Above Y=31	Nether wart noise ≥ 1.17	Nether Wart Block
				Otherwise	Crimson Nylium
Nether Wastes	Floor with depth[s 13]	Soul sand noise ≥ -0.012	Not erosion[s 7]	Surface between Y=30 and Y=35	Soul Sand
			Otherwise		Netherrack
	Floor[s 2]	Above Y=31 and surface below Y=35	Gravel layer noise ≥ -0.012	Above Y=32	Gravel
				Not erosion[s 7]
Otherwise					Netherrack

The End

Conditions					Result block
Always					End Stone

Carvers

Carvers include carver caves and carver canyons. As the name suggest, they "carve" through the ground.

Carver caves and carver canyons are configured to have different probability to be generated in each chunk. If the carver generates, it carves through the ground in random directions starting at the configured start Y level:

• Carver caves generate from Y=-56 to Y=180. The probability of cave generation is higher at Y=-56 to Y=47. Carver caves sometimes include a main room and can have branches.
  • Nether carver caves generate Y=0 to Y=126.
• Canyons can start at levels 10 to 72.

• 
  A carver cave in the Overworld with a main room.
• 
  Soul Sand Valley with a Nether carver cave.
• 
  A canyon in the Overworld.

Structures

Structures are grouped into structure sets. A structure set determines the placement positions of the structures and places a structure at these positions based on the biome. If no structure matches the biome, then no structure is placed at a given position. The structure positions are usually calculated based on the spacing, separation, and frequency parameters of the structure set. Spacing determines the average distance between structure placement position in chunks, and separation determines the minimum distance. Frequency controls the probability that a determined position is used. If the biome at the placement attempt does not match the requirement, the structure is not placed. An exception are strongholds in Java Edition, which are placed as concentric rings, see Stronghold#Generation.

The following table gives the placement parameters for each structure set, as they are in Java Edition.

Structure Set	Spacing	Separation	Frequency	Structure	Weight	Required Biomes
Ancient Cities	24	8	100%	Ancient City	1	Deep dark
Buried Treasures	1	0	1%	Buried Treasure	1	Beach, Snowy Beach
Desert Pyramids	32	8	100%	Desert Pyramid	1	Desert
End Cities	20	11	100%	End City	1	End Midlands, End Highlands
Igloos	32	8	100%	Igloo	1	Snowy Taiga, Snowy Plains, Snowy Slopes
Jungle Temples	32	8	100%	Jungle Pyramid	1	Jungle, Bamboo Jungle
Mineshafts	1	0	0.4%	Mineshaft	1	many biomes
				Badlands Mineshaft	1	Badlands, Eroded Badlands, Wooded Badlands
Nether Complexes	27	4	100%	Fortress	2	Any Nether biome
				Bastion Remnant	3	Crimson Forest, Nether Wastes, Soul Sand Valley, Warped Forest
Nether Fossils	2	1	100%	Nether Fossil	1	Soul Sand Valley
Ocean Monuments	32	5	100%	Ocean Monument	1	Deep Oceans [st 1]
Ocean Ruins	20	8	100%	Cold Ocean Ruins	1	Frozen Ocean, Frozen Ocean, Cold Ocean, Ocean, Deep Frozen Ocean, Deep Cold Ocean, Deep Ocean
				Warm Ocean Ruins	1	Lukewarm Ocean, Warm Ocean, Deep Lukewarm Ocean
Pillager Outposts	32	8	20% [st 2]	Pillager Outpost	1	Desert, Plains, Savanna, Snowy Plains, Taiga, Grove, Meadow, Frozen Peaks, Jagged Peaks, Stony Peaks, Snowy Slopes, Cherry Grove
Ruined Portals	40	15	100%	Ruined Portal	1	See Ruined Portal#Generation Together: All Overworld biomes
				Desert Ruined Portal	1
				Jungle Ruined Portal	1
				Swamp Ruined Portal	1
				Mountain Ruined Portal	1
				Ocean Ruined Portal	1
				Nether Ruined Portal	1	All Nether biomes
Shipwrecks	24	4	100%	Shipwreck	1	Any ocean
				Beached Shipwreck	1	Beach, Snowy Beach
Strongholds	N/A [st 3]		100%	Stronghold	1	All Overworld biomes [st 4]
Swamp Huts	32	8	100%	Swamp Hut	1	Swamp
Trail Ruins	34	8	100%	Trail Ruins	1	Taiga, Snowy Taiga, Old Growth Pine Taiga, Old Growth Spruce Taiga, Old Growth Birch Forest, Jungle
Villages	34	8	100%	Plains Village	1	Plains, Meadow
				Desert Village	1	Desert
				Savanna Village	1	Savanna
				Snowy Village	1	Snowy Plains
				Taiga Village	1	Taiga
Woodland Mansions	80	20	100%	Woodland Mansion	1	Dark Forest,Pale Garden

Once a structure start has been determined, the structure itself is generated. First, the layout of the pieces is determined. This also happens in the structure_starts generation step. Since structures can spread across many chunks, the entire structure has to be generated as soon as any chunk the structure could reach is fully generated. The resulting piece positions are stored in the chunk of the structure start. Other chunks store a reference to the chunk that stores the structure pieces. When a chunk is generating its decoration in the features step, the stored pieces are placed in the world (see #Features).

Features

The generation of features and placement of structure pieces (see #Structures) happens in the same step and are called decorations collectively. Each biome has a list of allowed features and structures that are possible to generate in them.

Decoration steps

Features and structures generate in 11 steps after each other called decoration steps.

1. raw_generation: Small end islands
2. lakes: Lava lakes
3. local_modifications: Amethyst geodes and icebergs
4. underground_structures: Trial chambers, buried treasure, mineshafts, trail ruins, monster rooms and fossils
5. surface_structures: All other structures, desert wells and blue ice patches
6. strongholds: Unused, strongholds use the surface_structures step
7. underground_ores: Ore blobs and sand/gravel/clay disks
8. underground_decoration: Infested block blobs, nether gravel and blackstone blobs, and all nether ore blobs
9. fluid_springs: Water and lava springs
10. vegetal_decoration: Trees, bamboo, cacti, kelp, and other ground and ocean vegetation
11. top_layer_modification: Freeze top layer feature

Generation

To generate features in a chunk, the game first determines a list of biomes that appear in that chunk or the 8 surrounding chunks. Using that biome list the game constructs a list of features that are possible to generate in those biomes. For each decoration step, first the matching structure pieces are placed, followed by the features. When a structure piece crosses a chunk border, only the part in the current chunk is placed. Each feature has its own placement rules including the number of placement attempts and where in the chunk should the feature try to be placed. The game follows the rules to select a block in the chunk then checks if the biome, block and its surroundings at the current position allows that feature to spawn, and if so places the feature. Features can place block outside the current chunk's boundaries but are limited in the nearby 3×3 area.

When features are generated, they can spill over into neighboring chunks that have already had their features generated. Thus, the feature order specified above is not always adhered to. It is therefore also possible for two worlds generated with the same seed, from the same version of Minecraft, to differ slightly depending on the players' travel routes, because the chunk generation order may determine which of two conflicting features overwrite or suppress the other.

Lighting

As one of the last steps of chunk generation, the light levels for each block are calculated. Before this step, no block placement updates light, and light updates are instead deferred to this step.

Mob spawning

In Java Edition many animals generate upon initial chunk creation. One in ten newly-generated chunks attempts to generate animal mobs, usually in packs of up to 4 of the same species.

In Bedrock Edition animals do not spawn during chunk generation, but they continually attempt to spawn as part of the environmental spawning algorithm.

Notably, mobs that spawn with a structure (e.g. elder guardian in ocean monuments) are immediately spawned when the structure is placed and are not spawned in this step.

Heightmaps

In Java Edition, heightmaps are technically calculated at every step of world generation. Before features are placed, there are only 2 heightmaps – OCEAN_FLOOR_WG and WORLD_SURFACE_WG. After feature placement, OCEAN_FLOOR, WORLD_SURFACE, MOTION_BLOCKING and MOTION_BLOCKING_NO_LEAVES are calculated.

Videos

Videos by Henrik Kniberg:

History

A world generation algorithm has been included in the game since its very inception. World generation was often changed significantly before the Java Edition's release. Notably, after its release, world generation has changed greatly in Java Edition 1.7.2 and Java Edition 1.18. For Bedrock Edition, significant changes were made in Pocket Edition v0.9.0 alpha and Bedrock Edition 1.18.0.

You may find more information on this topic at the History subpage.

References

External links

• More information on xoroshiro128++, the PRNG algorithm Minecraft uses for Overworld generation by University of Milan
• More information on Perlin noise by Raouf Touti

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