Brian Neumann-FopianoIris
Iris is a world generation engine for Minecraft servers and mod loaders. It generates terrain, biomes, caves, structures, objects, and entities from editable JSON packs, with a full in-game studio authoring workflow. The same engine runs as a Bukkit-family plugin and as a Fabric, Forge, or NeoForge server mod, and produces bit-identical terrain on every platform for the same pack and seed. The master branch targets the current Minecraft version (26.2).
Support | Documentation | Git
Consider supporting development by buying Iris on Spigot.
Language and localization
Canonical English is defined in the typed Java catalogs under core/src/main/java/art/arcane/iris/core/localization, next to the command, Studio, runtime, and UI surfaces that use it. Iris does not ship an English server translation file; the required Minecraft client asset remains at assets/irisworldgen/lang/en_us.json. Complete server bundles and matching client assets are included for German, Spanish, Finnish, French, Hebrew, Italian, Japanese, Korean, Lithuanian, Dutch, Polish, Portuguese, Russian, Turkish, Vietnamese, Simplified Chinese, and Traditional Chinese. Set language in Iris settings to select one. A JSON file at languages/overrides/<locale>.json can override only selected server messages; omitted entries resolve from the bundle and then code-owned English.
Platforms
| Platform | Artifact | Minecraft | Notes |
|---|---|---|---|
| Paper / Purpur / Leaf / Canvas | plugin jar | 26.2 | Full feature set |
| Folia | plugin jar | 26.2 | Region-safe scheduling throughout |
| Spigot / CraftBukkit | plugin jar | 26.2 | Full feature set |
| Fabric | mod jar | 26.2 | Server worldgen + client HUD; requires Fabric Loader 0.19.3+ |
| Forge | mod jar | 26.2 | Server worldgen + client HUD; requires Forge 65.0.4+ |
| NeoForge | mod jar | 26.2 | Server worldgen + client HUD; requires NeoForge 26.2.0.12-beta+ |
Java 25 is required on every platform.
The modded feature set matches the plugin wherever the operation is not Bukkit-bound: worldgen
from Iris packs, authoring with mod blocks/items/entities (with validation suggestions), studio
workspaces with schema autocomplete over the server's live registries, entity spawning parity
including death loot, pregeneration with a boss bar or client HUD, the /iris command tree, and
the goldenhash determinism gate, which is interchangeable across all four platforms.
Install
Plugin (Paper/Purpur/Leaf/Canvas/Folia/Spigot): drop the plugin jar into plugins/ and start
the server. On first boot Iris downloads the default overworld pack automatically.
Mod (Fabric/Forge/NeoForge): drop the mod jar into mods/ and start the server. The jar is
self-contained (core, SPI, and required Fabric API modules are bundled). On first boot Iris
downloads the default overworld pack before the worldgen datapack is written, so the default
pack is fully active immediately. Packs installed later register their custom dimension types
(height ranges) and custom biomes through the forced datapack at server start — restart once after
adding a pack so worlds get its full heights and biomes; worlds created before that restart run
with fallback heights.
Singleplayer (modded clients): installed Iris packs appear as selectable World Types on the Create New World screen; the integrated server runs the same engine.
The client mod
Installing the mod jar on a client adds a native pregeneration HUD: a top-left panel with a
progress bar, chunks done/total, percent, chunks per second, and ETA, turning yellow while the
pregen is paused. The H key (rebindable, under the "Iris" controls category) toggles it.
The HUD works against modded Iris servers and against Bukkit/Paper Iris servers, both over the
irisworldgen:main channel (custom payloads on modded, plugin messaging on Bukkit). Vanilla
clients are unaffected and get the server-side boss bar instead; on non-Iris servers the client
mod is inert.
Quickstart
Create and enter an Iris world.
Plugin (optional arguments are keyed):
/iris create myworld type=overworld seed=1337
/iris load myworld
Mod (positional arguments):
/iris create myworld overworld 1337
Pregeneration requires a radius in blocks. On the plugin, optional arguments are keyed; on modded servers they are positional and composable:
/iris pregen start 352 world=myworld center=0,0 gui=false
/iris pregen start 352 irisworldgen:myworld at 0 0 sync
Players with the client mod see the native HUD; everyone else gets a boss bar (modded) or
console/status output. /iris pregen status reports progress on the plugin.
Studio and VSCode workspace
The studio is the pack authoring environment, available on all platforms. Studio worlds are transient — they are deleted on close and purged at startup.
/iris studio create <name> [template] scaffold a new pack (default template: example)
/iris studio open <pack> [seed] open a temporary studio world for live editing
/iris studio vscode [pack] write a .code-workspace with JSON schemas
/iris studio update [pack] regenerate the workspace schemas
/iris studio close close and discard the studio world
As in the quickstart, optional arguments are keyed on the plugin (seed=1234) and positional on
the mod.
The generated VSCode workspace wires per-type JSON schemas (dimensions, biomes, regions, objects,
loot, entities, snippets) for full autocomplete. Schemas are generated from the server's live
registries, so on modded servers block, item, entity, enchantment, and potion-effect completion
includes installed mod content (for example create:brass_ingot). Editing an open studio's pack
files hotloads the changes and regenerates the schemas.
PlaceholderAPI
Iris registers the iris expansion when PlaceholderAPI is enabled. Paths are dot-separated,
lowercase, and never contain an underscore. Every value is plain text: no colour codes, no unit
suffixes, no % character, . as the decimal separator, and no thousands grouping.
Three answers are possible. A path that is not in the list below returns nothing, so PlaceholderAPI
re-emits the literal %iris_...% and a typo stays visible. A known path with no value right now
returns ---. A real zero returns 0.
| Placeholder | Value |
|---|---|
%iris_available% |
true when the Iris terrain service is live |
%iris_world.available% |
true when the reading player is in an Iris world and a reading exists |
%iris_world.biome% |
Surface biome display name at the player, e.g. Hot Desert Dunes |
%iris_world.biome-key% |
Surface biome load key, e.g. desert/hot-dunes |
%iris_world.region% |
Region display name at the player |
%iris_world.region-key% |
Region load key |
%iris_world.dimension% |
Dimension (pack) load key of the player's world |
%iris_pregen.available% |
true while a pregeneration job is running |
%iris_pregen.world% |
World name the running job is pregenerating |
%iris_pregen.percent% |
Completion, 0.00 to 100.00, no % character |
%iris_pregen.eta% |
Estimated seconds remaining, whole number |
%iris_pregen.eta-text% |
Same estimate as 2m 5s or 1h 30m |
%iris_pregen.chunks% |
Chunks generated so far |
%iris_pregen.total% |
Chunks in the job |
%iris_pregen.chunks-per-second% |
Current rate |
%iris_pregen.paused% |
true while the job is paused |
The world values are the surface reading at the player's block column. Walking refreshes them at most
once per second per player, so a whole board of world.* keys costs one refresh per player per
second no matter how many of them are on it, and a value may lag a sprinting player by up to a
second. A jump that is not walking — joining, respawning, changing worlds, stepping through a portal,
or any teleport including /iris goto, /tp, an ender pearl and a random teleport — is published
immediately, so a player who arrives somewhere and then stands still never keeps reading the biome,
region or dimension of where they came from. pregen.* is global: there is one pregeneration job per
server, and %iris_pregen.world% says which world it is.
Migration from the pre-2.0 keys
The old underscore keys are gone. There is no alias and no dual-accept window; an old key now renders literally so it is visible rather than silently wrong.
| Old key | New key | Why |
|---|---|---|
%iris_biome_name% |
%iris_world.biome% |
Renamed onto the dot grammar |
%iris_biome_id% |
%iris_world.biome-key% |
Renamed; id was always the load key |
%iris_region_name% |
%iris_world.region% |
Renamed onto the dot grammar |
%iris_region_id% |
%iris_world.region-key% |
Renamed; id was always the load key |
%iris_biome_file% |
removed | Rendered an absolute server path into player-visible text, and threw on packs with no backing file |
%iris_region_file% |
removed | Same as biome_file |
%iris_world_seed% |
removed | Handed the world seed to anyone who could read a scoreboard, and a placeholder has no permission context to gate on |
%iris_terrain_height% |
removed | Reported the generated height, before objects and player edits, so it disagreed with the block under the player's feet |
%iris_terrain_slope% |
removed | Three extra noise samples per read for an unformatted pack-authoring diagnostic |
%iris_world_mode% |
removed | Studio or Production; a studio world exists for seconds during authoring and is never on a live board |
%iris_world_speed% |
removed | Mutated engine rate-window state every time it was read. %iris_pregen.chunks-per-second% answers the same question from a snapshot |
The old keys also read the cave biome for a player standing under an overhang, because they
sampled two blocks above the player's feet. The new world.biome is always the surface biome,
which is what a board reader means.
Building from source
Requirements: JDK 25 (set JAVA_HOME to it). The Gradle wrapper handles everything else.
./gradlew buildAllToOut
builds every platform artifact into dist/:
Iris v<version> [CraftBukkit] <mc>.jar
Iris v<version> [Fabric] <mc>+<loader>.jar
Iris v<version> [Forge] <mc>+<loader>.jar
Iris v<version> [NeoForge] <mc>+<loader>.jar
Per-platform tasks: ./gradlew buildBukkit, buildFabric, buildForge, buildNeoforge. The
developer SPI jar (the pure-JVM platform API contract) is built to spi/build/libs/ by
./gradlew :spi:jar.
If you need help compiling as a developer or contributor, ask in the Discord. Do not come to the Discord asking for free copies or a compile tutorial.