Server World Configuration

SteelMC world configuration is done through a TOML file located at config/worlds.toml. This page documents all world, domain, world generator and storage options.

Basic Settings

Option	Type	Default	Description
`save_path`	String	`"saves"`	Root directory for saved worlds
`seed`	String	`""`	World generation seed (empty = random)
`default_gamemode`	String	`"survival"`	Default gamemode for new player data
`difficulty`	String	`"normal"`	Difficulty for new level data
`storage.type`	Identifier	`"steel:disk"`	Default world storage backend
`player_storage.type`	Identifier	`"steel:file"`	Player data storage backend

The values seed, default_gamemode, difficulty and storage are inherited from root to domains and from domains to worlds. They can also be overridden in each place, which gives the server flexible configuration.

Valid gamemodes are survival, creative, adventure and spectator. Valid difficulties are peaceful, easy, normal and hard.

Unfortunately, Mojang is not consistent about using the same terms in their codebase. World, level and map can describe the same thing internally. Steel also adds some Multiverse functionality natively. To describe this clearly, Steel introduced a new term: domains. The glossary also covers dimension and world generator, which are used below.

Domains

At least one domain is needed, and exactly one domain needs to be the default.

[domains.minecraft]
default = true
seed = "example seed"
default_gamemode = "survival"
storage.type = "steel:disk"

Option	Type	Default	Description
`domains.<domain>.worlds`	Array	None	[REQUIRED] Worlds inside this domain
`domains.<domain>.default`	bool	`false`	Whether this is the default domain
`domains.<domain>.seed`	String	inherited	Domain seed override
`domains.<domain>.default_gamemode`	String	inherited	Domain gamemode override
`domains.<domain>.difficulty`	String	inherited	Domain difficulty override
`domains.<domain>.storage`	Table	inherited	Domain storage override

The domain name must be a valid identifier namespace. global is reserved and cannot be used.

Worlds

Each domain needs at least one world and exactly one default world.

[[domains.minecraft.worlds]]
name = "overworld"
generator = "minecraft:overworld"
default = true
storage.type = "steel:ram"

Option	Type	Default	Description
`name`	String	None	[REQUIRED] Name of the world inside the domain
`generator`	Identifier	None	[REQUIRED] World generator to use, options of world generator are in the next section
`default`	bool	`false`	Whether this is the default world of the domain
`seed`	String	inherited	World seed override
`default_gamemode`	String	inherited	World gamemode override
`difficulty`	String	inherited	World difficulty override
`storage`	Table	inherited	World storage override
`nether_portal_target`	String	automatic	Same-domain world name used by Nether portals from this world
`end_portal_target`	String	automatic	Same-domain End-dimension world name used by End portals from non-End worlds
`config`	Table	`{}`	Generator-specific config

World names must be valid identifier paths, cannot contain / and must be unique within the domain.

Portal Targets

Portals are resolved inside the source world’s domain. If no explicit target is configured, Steel uses vanilla conventional world names:

Nether portals from the_nether target overworld
Nether portals from any other world target the_nether
End portals from non-End worlds target the_end
End portal returns from End-dimension worlds use the entity or player’s respawn data instead of end_portal_target

The conventional names make a normal overworld, the_nether, and the_end setup work without extra config. If you use different world names, configure explicit targets.

[domains.minecraft]
default = true

[[domains.minecraft.worlds]]
name = "overworld2"
generator = "minecraft:overworld"
default = true
nether_portal_target = "the_nether2"
end_portal_target = "the_end2"

[[domains.minecraft.worlds]]
name = "the_nether2"
generator = "minecraft:the_nether"
nether_portal_target = "overworld2"

[[domains.minecraft.worlds]]
name = "the_end2"
generator = "minecraft:the_end"

Portal target fields take a world name, not a full namespace:path identifier. They cannot point across domains, cannot point to the same world, and must point to a declared world in the same domain. end_portal_target is invalid on worlds using the End dimension, and it must point to a world whose generator uses the End dimension.

Generators

Steel has these built-in world generators:

Generator	Config
`minecraft:overworld`	No config table accepted
`minecraft:the_nether`	No config table accepted
`minecraft:the_end`	No config table accepted
`minecraft:flat`	Optional flat-world config
`steel:empty`	Requires `config.dimension_type`

Minecraft world generator

The generators minecraft:overworld, minecraft:the_nether and minecraft:the_end have no config. They produce vanilla-parity worlds for their dimensions.

Flat world generator

The world generator minecraft:flat accepts an optional config table. Without it, Steel uses the Overworld dimension, a vanilla-style superflat layer stack and the default structure overrides.

Option	Type	Default	Description
`layers[].block`	Identifier	None	[REQUIRED] Block used by this layer
`layers[].height`	Integer	None	[REQUIRED] Height of this layer, must be greater than `0`
`dimension_type`	Identifier	`"minecraft:overworld"`	Dimension type used by the flat world
`layers`	Array of layer tables	bedrock 1, dirt 2, grass block 1	Blocks generated from bottom to top
`features`	Boolean	`false`	Whether to generate decoration features. `true` is not implemented yet
`lakes`	Boolean	`false`	Whether to generate lakes. `true` is not implemented yet
`structure_overrides`	Identifier array	strongholds and villages	Structures allowed in this flat world

The default layers are minecraft:bedrock with height 1, minecraft:dirt with height 2 and minecraft:grass_block with height 1. The default structure_overrides are minecraft:strongholds and minecraft:villages.

Custom layers can be written with repeated layer tables or inline layer tables.

Repeated layer tables

[domains.dev]
default = true

[[domains.dev.worlds]]
name = "flat"
generator = "minecraft:flat"
default = true

[domains.dev.worlds.config]
features = false
lakes = false
structure_overrides = ["minecraft:villages"]

[[domains.dev.worlds.config.layers]]
block = "minecraft:bedrock"
height = 1

[[domains.dev.worlds.config.layers]]
block = "minecraft:grass_block"
height = 3

Inline layer tables

[domains.flat]
default = true

[[domains.flat.worlds]]
name = "overworld"
generator = "minecraft:flat"
default = true

[[domains.flat.worlds]]
name = "the_nether"
generator = "minecraft:flat"
config.dimension_type = "minecraft:the_nether"
config.layers = [
  { block = "minecraft:bedrock", height = 1 },
  { block = "minecraft:blackstone", height = 2 },
  { block = "minecraft:netherrack", height = 1 }
]

[[domains.flat.worlds]]
name = "the_end"
generator = "minecraft:flat"
config.dimension_type = "minecraft:the_end"
config.layers = [
  { block = "minecraft:bedrock", height = 1 },
  { block = "minecraft:end_stone", height = 3 }
]

Empty world generator

The important part of an empty world generator is the config, which defines dimension_type. That field selects the dimension and its properties, such as Y height and fog.

[domains.empty]
default = true
storage.type = "steel:ram"

[[domains.empty.worlds]]
name = "void"
generator = "steel:empty"
default = true

[domains.empty.worlds.config]
dimension_type = "minecraft:overworld"

Storage

Steel has these built-in world storage backends. Storage can be set for the full server, per domain and per world. For example, the full server can use RAM storage, one domain can still use disk storage and be saved to disk, and a world in that domain can still use RAM storage. This gives maximum flexibility to configure storage as needed.

Storage	Config
`steel:disk`	Optional `config.path`, relative to `save_path`
`steel:ram`	No config, chunks are not saved

Player storage currently only supports steel:file.

Example disk path override:

[[domains.minecraft.worlds]]
name = "testing"
generator = "minecraft:overworld"

[domains.minecraft.worlds.storage]
type = "steel:disk"

[domains.minecraft.worlds.storage.config]
path = "custom/testing"

Example Configuration

This section first shows the default config generated on first start. The second config uses the concepts above to construct a setup with three domains, different gamemodes, storage settings and world generator config.

Simple configuration

This is the default config for worlds.toml, which creates a normal survival world.

# Root defaults inherited by domains and worlds unless overridden.
save_path = "saves"
seed = ""
default_gamemode = "survival"
difficulty = "normal"

[storage]
type = "steel:disk"

[player_storage]
type = "steel:file"

[domains.minecraft]
default = true

# Worlds may optionally set same-domain `nether_portal_target` and
# `end_portal_target` fields to override the vanilla conventional names.
[[domains.minecraft.worlds]]
name = "overworld"
generator = "minecraft:overworld"
default = true

[[domains.minecraft.worlds]]
name = "the_nether"
generator = "minecraft:the_nether"

[[domains.minecraft.worlds]]
name = "the_end"
generator = "minecraft:the_end"

Extended Multidomain configuration

This has many different settings, which are explained above. Currently, the minecraft domain is on disk, as is the world the_nether from the flat domain. The empty and minecraft domains use survival gamemode, while the flat domain uses creative gamemode.

save_path = "saves"
seed = ""
default_gamemode = "survival"
difficulty = "normal"

[storage]
type = "steel:disk"

[player_storage]
type = "steel:file"

[domains.minecraft]
default = true

[[domains.minecraft.worlds]]
name = "overworld"
generator = "minecraft:overworld"
default = true

[[domains.minecraft.worlds]]
name = "the_nether"
generator = "minecraft:the_nether"

[[domains.minecraft.worlds]]
name = "the_end"
generator = "minecraft:the_end"

[domains.flat]
default_gamemode = "creative"
storage.type = "steel:ram"

[[domains.flat.worlds]]
name = "overworld"
generator = "minecraft:flat"
default = true

[[domains.flat.worlds]]
name = "the_nether"
generator = "minecraft:flat"
config.dimension_type = "minecraft:the_nether"
config.layers = [
    { block = "minecraft:bedrock", height = 1 },
    { block = "minecraft:blackstone", height = 2 },
    { block = "minecraft:netherrack", height = 1 }
]
storage.type = "steel:disk"

[[domains.flat.worlds]]
name = "the_end"
generator = "minecraft:flat"
config.dimension_type = "minecraft:the_end"
config.layers = [
    { block = "minecraft:bedrock", height = 1 },
    { block = "minecraft:end_stone", height = 3 }
]

[domains.empty]
default = false
storage.type = "steel:ram"

[[domains.empty.worlds]]
name = "empty"
default = true
generator = "steel:empty"

[domains.empty.worlds.config]
dimension_type = "minecraft:overworld"

Validation Rules

The server validates world configuration on startup:

unknown fields are rejected
at least one domain must be declared
exactly one domain must set default = true
each domain must declare at least one world
each domain must have exactly one default world
domain names must be valid identifier namespaces
the domain name global is reserved
world names must be valid identifier paths and cannot contain /
save_path and storage paths must be clean relative paths
generators and storage backends must be known to Steel
nether_portal_target and end_portal_target must point to an existing same-domain world and cannot target the source world
end_portal_target cannot be set on End-dimension worlds
end_portal_target must target an End-dimension world
minecraft:flat requires at least one layer, and features = true or lakes = true are not implemented yet

If validation fails, the server will exit with an error message.

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