Minecraft Wiki
This article is about the modern custom world type. For the world type before Java Edition 1.13, see Old Customized. For the Easter egg dimensions in Java Edition 20w14∞, see Java Edition 20w14∞ § World generation.
"Custom world" redirects here. For creating custom dimensions, see Custom dimension. For controlling world generation using data packs, see Custom world generation.
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This feature is exclusive to Java Edition. 

Custom is a world type that allows users to change the generation of the Overworld, Nether, and End dimensions as well as the ability to create custom dimensions. It is edited using a JSON file that is imported on the world creation screen.


Custom world generation works using JSON files, which need to be imported before world creation.

In the world creation menu, go to more options and select the "Import World" option. Then, select a world generation JSON file. A warning appears saying that custom worlds are experimental. Click "Yes" to continue.

The only way to access added dimensions is through commands, such as /execute in <dimension name> run tp @s ~ ~ ~, which teleports the player to the specified dimension (see § JSON format).

JSON format[]

Jigsaw Block (top texture) JE2 BE2.png
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Instructions: explanations on each component of the JSON file. Useful sources: [1], [2]

Custom generation files take the following format:

  • The root tag.
    •  bonus_chest (Boolean): Whether the world has a bonus chest or not (equivalent to the "Bonus chest" option).
    •  generate_features (Boolean): Whether structures should be generated or not (equivalent to the "Generate structures" option).
    •  seed (integer): The numerical seed of the world.
    •  legacy_custom_options (string): The custom world preset that was used to generate the world when it was an old customized world. Exists only for old customized worlds.
    •  dimensions: A list of the dimensions in this world where the key is the namespace ID of the dimension.
      • A dimension. The dimensions minecraft:overworld, minecraft:the_nether and minecraft:the_end are required for a well functioning world. Any other namespaced ID is allowed for custom dimensions.
        •  generator: Generation settings used for that dimension.
          •  type (string): The ID of the generator. Can be minecraft:flat for a superflat dimension, minecraft:noise for noise generation, or minecraft:debug for a debug dimension.
          • Other compounds (see below)
        •  type: This can be a list of options for the dimensions, the namespaced ID of a dimension type file in a data pack, or one of the four default dimension types (minecraft:overworld, minecraft:the_nether, minecraft:the_end, minecraft:overworld_caves).
          •  name: The resource location used for the dimension type. Required only when importing world settings.
          •  ultrawarm: Whether the dimensions behaves like the nether (water evaporates and sponges dry) or not. Also lets stalactites drip lava and causes lava to spread faster and thinner.
          •  natural: When false, compasses spin randomly, and using a bed to set the respawn point or sleep, is disabled. When true, nether portals can spawn zombified piglins.
          •  coordinate_scale: The multiplier applied to coordinates when leaving the dimension.
          •  has_skylight: Whether the dimension has skylight access or not.
          •  has_ceiling: Whether the dimension has a bedrock ceiling or not.
          •  ambient_light: How much light the dimension has, default is 0.5 in the demo file (for upper and lower bounds as well as precise effect[needs testing]).
          •  fixed_time (optional): Can be false or any integer from 0 to 24000. If this is set to a number, the time of the day is the specified value. However, in at least some worlds,[needs testing] false is interpreted as 0, giving constant sunrise. To ensure a normal time cycle, leave the attribute undefined (i.e, do not include it).
          •  piglin_safe: Whether piglins shake and transform to zombified piglins.
          •  bed_works: When false, the bed blows up when trying to sleep.
          •  respawn_anchor_works: Whether players can charge and use respawn anchors.
          •  has_raids: Whether players with the Bad Omen effect can cause a raid.
          •  logical_height: The maximum height to which chorus fruits and nether portals can bring players within this dimension. This excludes portals that were already built above the limit as they still connect normally. May not be greater than height.
          •  min_y: The minimum height in which blocks can exist within this dimension. Should be between -2032 and 2031 and be a multiple of 16 (effectively making 2016 the maximum). Setting it lower than -2048 will only allow the temporary placement of blocks below it as they won't be saved. Furthermore, lighting won't work correctly at Y-coordinate -2048 and below.[1]
          •  height: The total height in which blocks can exist within this dimension. Should be between 0 and 4064 and be a multiple of 16. It can be set higher than the maximum by the same amount of temporary layers + 16. Max y = min y + height, and may not be more than 2032.
          •  infiniburn: A resource location defining what block tag to use for infiniburn.
          •  effects: Can be "minecraft:overworld", "minecraft:the_nether" and "minecraft:the_end". Determines the dimension effect used for this dimension. Setting to overworld makes the dimension have clouds, sun, stars and moon. Setting to the nether makes the dimension have thick fog blocking that sight, similar to the nether. Setting to the end makes the dimension have dark spotted sky similar to the end, ignoring the sky and fog color. If undefined, the value will be automatically set to "minecraft:overworld".

Generator types[]

The format of the  generator compound is dependent on the value of its generator ID, or  type.

When the generator ID type is minecraft:noise:

  •  generator: Generation settings used for the dimension.
    •  type: The ID of the generator (in this case, minecraft:noise).
    •  seed: The seed used to generate the dimension. In most cases, this is exactly the same as the world seed, but can be different and the dimension generated is based upon this seed and not the world seed.[needs testing]
    •  settings: The noise settings used in the terrain generator. Can be set to a string to use a preset defined in the worldgen/noise_settings folder with a list of customized options. See Custom world generation#Noise settings for more information.
    •  biome_source: Settings dictating which biomes and biome shapes.
      •  type: The type of biome generation. Arguments lie in the biome_source compound. One of multi_noise, fixed, checkerboard, or the_end.
        • If type is multi_noise: 3D biome generation used in the nether, and in the overworld in snapshot 21w37a and after.[needs testing]
          •  preset: A preset of the set of biomes to be used, mutually exclusive with  biomes. One of nether or overworld.
          •  biomes: A list of biomes, including their target noise parameters.
            • : A biome and its properties
              •  biome: The biome. A single biome ID may be repeated several times with different parameters.
              •  parameters: Represent optimal conditions for where the biome should be placed. These values do not affect the generation of terrain within biomes, they affect where the game chooses to place biomes. At any specific point, the biome having parameters most closely resembling the respective parameter on each noise map at that point is chosen. For example, if the point were to have values of -1 temperature, 0.2 humidity, 0.5 altitude and 0 weirdness then birch_forest_hills (-0.1t,0.2h,0.25a,0w) would be chosen over desert (0.5t,-0.5h,0a,0w). Parameter combinations should be unique in the biomes list, otherwise only the first biome entry will generate.
                •  temperature: Used to place similar biomes near each other. Not to be confused with the temperature value listed on Biome.
                •  humidity: Used to place similar biomes near each other.
                •  continentalness: Low continentalness corresponds to ocean terrain, high continentalness to inlands terrain.
                •  erosion: In the overworld, high erosion corresponds to flat terrain.
                •  weirdness: Used for biome rarity.[verify]
                •  depth: Used to generate cave biomes. This is the only parameter that can vary when moving vertically. A depth of 0 is at the surface, a depth of 1 is at 128 blocks below the surface.
                •  offset: Similar to the other parameters but offset is 0 everywhere, thus setting this parameter nearer to 0 gives the biome a greater edge over others, all else being equal. Increasing this makes the biome rarer, without altering the biome placement.
          •  min_quart_y: [needs testing]
          •  max_quart_y: [needs testing]
            •  firstOctave: The octave the first amplitude in the list is associated with. Lower values make the whole amplitudes sequence affect lower frequencies (smoother). Incrementing it by 1 doubles the frequency of the base octave.
            •  amplitudes: The amplitudes of consecutive octaves. Octaves further down the list have higher frequencies (double at each step). Higher octaves have intrinsically lower amplitudes in Perlin noise. This list further modifies the amplitudes by making low/high frequency features more or less pronounced. The resultant Perlin noise value at a certain coordinate is not just a simple sum of the independent components.[verify]
              • An amplitude. Setting one to 0 effectively disables that frequency component.[verify]
          •  large_biomes: Whether the biomes are large. True for biomes generation in the "Large Biomes" world type.
          •  legacy_biome_init_layer: Whether the world was default_1_1.[needs testing]
        • If type is the_end: Biome generation used in the end with biome minecraft:the_end in the center and other end biomes around.
        • If type is fixed: a single biome.
          •  biome: The single biome to generate.
        • If type is checkerboard: A biome generation in which biomes are square (or close to square) and repeat along the diagonals.
          •  biomes: A list of biomes that repeat along the diagonals (can be more than 3).
          •  scale: Determines the size of the squares on an exponential scale. Range: (0 to 62).

When the generator ID type is minecraft:flat (used for Superflat world generation):

  •  generator: Generation settings used for the dimension.
    •  type: The ID of the generator (in this case, minecraft:flat).
    •  settings: Superflat settings.
      •  layers: Layer settings.
        • : A superflat layer. This list is interpreted from top to bottom, starting at bedrock level.
          •  height: The number of blocks in the layer.
          •  block: The block the layer is made of.
      •  biome: the single biome of the world
      •  lakes (optional): Whether or not to generate lakes. If set to true, then water and lava lakes generate often even in biomes where lakes don't normally generate. Lava lakes generate surrounded by different types of stone and ores from the overworld.
      •  features (optional): Whether or not to generate biome-specific decorations like trees, grass, flowers, cacti, etc.
      •  structures: Structure settings
        •  stronghold: Settings for how strongholds should be spawned. The stronghold values under the structures tag appear to be placeholders so that every namespaced structure has a value; these values are the ones that actually control stronghold spawning.
        •  structures: List of structures to use in this dimension
          •  <namespaced id>: The key for this field should be the namespaced ID of a structure, a list is available at Java Edition data value § Structures. If structures are not listed, it does not generate.
            •  spacing: Average distance between two structure placement attempts of this type in chunks[note 1].
            •  separation: Minimum distance between two structures of this type in chunks. Must be less than spacing.
            •  salt: [needs testing] A number that assists in randomization; see salt (cryptography).

When the generator ID type is minecraft:debug (used for Debug world generation):

  •  generator: Generation settings used for the dimension.
    •  type: The ID of the generator (in this case, minecraft:debug).


Moved to Custom world generation#Noise settings

Noise generator preset defaults[]

These are the settings used by the 6 presets available for the minecraft:noise generator.

Structure defaults[]

These are the default values for all namespaced structures. Every preset uses the same values for all of these structures, with the exception of minecraft:ruined_portal.

*Placeholder values, have no effect

**Salt values aren't used for theses structures; changing them produces no effect

Biome parameter defaults[]

These are the default values used for each biome in the multi_noise biome_source. Interestingly, although only the values for nether biomes are accessible through a preset, several overworld biomes have default values as well.

Type defaults[]

These are the settings used by the 3 dimensions present in Vanilla and the additional Overworld Caves settings provided by Minecraft.


Jigsaw Block (top texture) JE2 BE2.png
This section needs expansion. 
You can help by expanding it.
Instructions: more examples and the actual info for what the default generator uses.

Default settings[]

The following is the settings for an exported default Minecraft world.

Expanded default settings[]

This file contains the same settings used to produce a default world, but with all of the presets expanded to their default values. Note that there is a bug that makes it impossible to create the ender dragon fight without using the dimension type preset minecraft:the_end, as the flag that creates the fight is hardcoded and not accessible through JSON. However, it is otherwise identical to the default world.

Custom superflat dimension[]

An overview of a world made with the adjacent settings.

This dimension is a Superflat world with a layer of grass on four layers of coarse dirt on top of five layers of basalt. The entire world is full of village houses as spacing is set to 3 (default: 32) and separation is set to 1 (default: 8). The world starts by default at time 1000.


Java Edition
May 15, 2018The return of customized worlds was mentioned.[2][3][4]
1.1620w21aAdded custom worlds.
Custom worlds are JSON-driven.
Custom dimensions can be added and vanilla dimensions can be modified.
There is currently no in-game menu to modify worlds; custom worlds can be generated only by importing a JSON file.
pre1The "temparature" biome parameter is now spelled "temperature".
Dimensions and dimension settings can be created through data packs.
1.16.220w28aExperimental custom biome support is now included in custom worlds.
1.1720w49aMax build heights and bedrock ceiling heights are now customizable over 256 blocks via custom json files.
21w05aMinimum and maximum y values changed from -2047 and 2047 to -2032 and 2032.


Issues relating to "Custom" are maintained on the bug tracker. Report issues there.


External links[]

See also[]


  1. Setting this to a number does not mean one structure is generated this often, only that the game attempts to generate one; biomes or terrain could lead to the structure not being generated. The maximum distance of structure placement attempts is 2*spacing - separation.


  1. MC-194878
  2. "Customized worlds will be returning. I can't speak for the extra options you mentioned though." – u/AlmightyZing
    "But after 1.13"u/_Grum on Reddit, May 15, 2018
  3. "Would you really not consider holding off 1.13 until customised worlds are finished? Seems pretty crazy to set a precedent for the chance of losing features for several updates.
    We came so close to having access to customising structures in world gen this update too, a shame that hasn't made the cut" – u/DaUltraMarine
    "No, they will come back but completely different from before."u/_Grum on Reddit, May 15, 2018
  4. "No customization until after 1.13, or the other things?" – u/Kobbett
    "No more screens with 50 vague sliders indeed."u/_Grum on Reddit, May 15, 2018