RemapIDs

Data-driven registry remap and alias system for Minecraft modpack developers. Redirect any block, item, fluid, entity type, tag, recipe, or loot table ID to another — no code required.

Supported platforms: Forge 1.20.1 · Fabric 1.20.1 · NeoForge 1.21.1 · Fabric 1.21.1

Use Cases

• Removed a mod from your modpack? Remap its block/item IDs to equivalents from another mod so existing worlds don't lose data.
• Consolidating duplicate items? Redirect one mod's silver ingot to another mod's silver ingot across all recipes, loot tables, and tags.
• Replacing vanilla content? Remap vanilla blocks/items to modded equivalents — copper blocks become brass blocks, etc.
• Migrating pre-1.13 worlds? Use numerical IDs (e.g. 35:14) as sources — they're resolved via a built-in flattening table.

Getting Started

1. Install the mod

Drop the jar for your loader into your mods/ folder.

2. Create remap files

Create JSON files in config/remapids/remaps/. Each file contains a remaps array:

{
  "remaps": [
    {
      "source": "iceandfire:silver_ingot",
      "target": "othermod:silver_ingot",
      "types": ["item", "recipe", "loot_table", "tag"]
    }
  ]
}

3. Restart the game

Remaps are applied during startup. Registry-level remaps (block, item, fluid, entity_type) require a full restart. Recipe, loot table, and tag remaps can be reloaded with /reload.

Remap File Format

Each entry in the remaps array has:

Field	Required	Description
source	Yes	The ID to remap from (e.g. iceandfire:silver_ingot)
target	Yes	The ID to remap to (e.g. othermod:silver_ingot)
types	No	Array of remap types to apply. If omitted, applies to all applicable types.

Remap Types

Registry types (applied at startup, require restart):

Type	Description
block	Block registry — affects placed blocks in the world
item	Item registry — affects items in inventories
fluid	Fluid registry
entity_type	Entity type registry

Reloadable types (applied on datapack load, supports /reload):

Type	Description
recipe	Rewrites recipe JSON — ingredient and result item IDs
loot_table	Rewrites loot table JSON — item and block references
tag	Rewrites tag entries — redirects tag membership

Examples

Remove a mod and remap to alternatives

{
  "remaps": [
    {
      "source": "silents_mechanisms:copper_ingot",
      "target": "create:brass_ingot",
      "types": ["item", "recipe", "loot_table", "tag"]
    },
    {
      "source": "silents_mechanisms:copper_block",
      "target": "create:brass_block",
      "types": ["item", "block", "recipe", "loot_table", "tag"]
    }
  ]
}

Replace vanilla blocks with modded equivalents

{
  "remaps": [
    {
      "source": "minecraft:copper_block",
      "target": "create:brass_block",
      "types": ["item", "block"]
    },
    {
      "source": "minecraft:copper_ingot",
      "target": "create:brass_ingot",
      "types": ["item"]
    }
  ]
}

Wildcard remaps

Remap all items matching a pattern. Both source and target must contain *:

{
  "remaps": [
    {
      "source": "iceandfire:silver_*",
      "target": "othermod:silver_*"
    }
  ]
}

Pre-1.13 numerical IDs

Use numerical block/item IDs from pre-flattening Minecraft:

{
  "remaps": [
    {
      "source": "35:14",
      "target": "minecraft:red_wool",
      "types": ["block"]
    }
  ]
}

Custom numerical ID mappings for modded pre-1.13 IDs can be added in config/remapids/numerical_ids.json.

Tag remaps

Prefix tag sources with #:

{
  "remaps": [
    {
      "source": "#forge:ores/silver",
      "target": "#forge:ores/tin",
      "types": ["tag"]
    }
  ]
}

Chain Resolution

Remap chains are automatically flattened. If A → B and B → C are both defined, A resolves directly to C. Circular chains are detected and rejected. Maximum chain depth is 10.

Commands

Command	Description
/remapids id block	Shows the registry ID of the block you're looking at, including any active remaps
/remapids id hand	Shows the registry ID of the item in your main hand, including any active remaps

How It Works

RemapIDs operates at multiple levels depending on the remap type:

• Registry aliases (block, item, fluid, entity_type): Injects aliases into the game registry's internal lookup maps so the source ID resolves to the target's registry entry. On Forge, also redirects ForgeRegistry.getValue() lookups.
• Block state remapping: When aliasing blocks, block state IDs in Block.BLOCK_STATE_REGISTRY are remapped so network serialization uses the target block's state IDs. Compatible block state properties (e.g. axis, waterlogged) are preserved.
• JSON rewriting (recipe, loot_table): Rewrites datapack JSON at load time, replacing item, block, and tag references.
• Tag rewriting (tag): Intercepts tag loading to redirect tag entries.
• NBT interception (Fabric/NeoForge): Intercepts block state and item stack deserialization from NBT for world migration.
• Missing mappings (Forge): Handles MissingMappingsEvent for world migration when a source mod is removed.

File Structure

config/
└── remapids/
    ├── remaps/              ← Drop remap JSON files here
    │   ├── create_compat.json
    │   ├── old_mod_removal.json
    │   └── ...
    └── numerical_ids.json   ← Optional: custom pre-1.13 ID mappings

Multiple JSON files are supported — they're loaded alphabetically and merged. This lets you organize remaps by mod or purpose.

License

See modding licence.