Inventory Weights Items Configuration

WARNING

MT Inventory Weight no longer uses the old ItemWeightConfigItems class, the old inventory_weights_items.json file, or any item-specific inventory_weights_items.toml config file.

Item-specific weights are now handled by a data-driven datapack system.

If you had custom item weights in an old JSON/TOML config, you must migrate them into datapack JSON files.

Specific item weight overrides are now handled with datapacks.

General item category weights are handled by the server config through fzzy_config.

Ways to Customize Item Weights

There are four main ways to customize weights:

1. Server config category weights
2. Datapack item overrides
3. Datapack NBT-specific rules
4. Add-ons using the public API

Server Category Weights

Broad item categories are configured in:

config/inventoryweight/server-config.toml

These values control default/fallback weights for categories such as:

• buckets
• bottles and potions
• blocks
• ingots, gems, alloys, and shards
• nuggets
• generic items
• creative/technical items

For full details, see the Server Configuration page.

Datapack Item Weights

Specific item weights should be configured through datapacks.

Item weight files go here:

data/<namespace>/inventory_weight/items/*.json

Example file:

data/my_pack/inventory_weight/items/vanilla_overrides.json

Example content:

{
  "minecraft:stone": 260.0,
  "minecraft:diamond": {
    "weight": 120.0
  }
}

In this example:

• minecraft:stone has a weight of 260.0
• minecraft:diamond has a weight of 120.0

Array Format

Datapacks can also use an array format:

[
  {
    "item": "minecraft:stone",
    "weight": 260.0
  },
  {
    "item": "minecraft:diamond",
    "weight": 120.0
  }
]

NBT-Specific Item Weights

NBT-specific rules allow different weights depending on item NBT.

Example:

{
  "minecraft:bundle": {
    "weightWhenNbt": {
      "Items": {
        "value": "minecraft:glass",
        "weight": 100.0
      }
    }
  }
}

This means a bundle with matching NBT data can receive a special weight.

Depending on the NBT structure, lists and string values can be checked.

Loading and Reloading

Datapack item weights are loaded:

• when the server starts
• when /reload is used

The server syncs resolved item weight data to clients so tooltips show the same values as the server.

Conflict Handling

If the same item is defined in multiple datapack files, MT Inventory Weight logs a warning.

The first loaded definition is kept.

WARNING

Avoid defining the same item weight in multiple datapacks unless you know which datapack load order will win.

Containers and Backpacks

Supported shulkers and backpacks use special weight handling.

Current rule:

final container weight = empty container weight + weight inside / 2

Tooltips show:

Weight inside: %s
Weight: %s

Weight inside is the full uncompressed contents weight.

Weight is the effective weight used by the player weight system.

Default Automatic Weight Calculation

If an item does not have a datapack override, MT Inventory Weight calculates a fallback weight automatically.

The default calculation can consider:

• item category
• max stack size
• food value and saturation
• fireproof status
• durability
• armor protection
• tool durability
• item rarity
• block hardness
• block blast resistance
• block transparency
• slabs and stairs
• block entities

This allows most vanilla and modded items to work without manual configuration.

Add-on API

Mods can provide custom item weight logic through the public add-on API:

com.megatrex4.api.v1

Add-ons can register an ItemWeightProvider to calculate weights dynamically from item data, NBT, capabilities, or another mod's API.

See the Add-on API page for examples.

Example Datapack Structure

my_weight_pack/
├─ pack.mcmeta
└─ data/
   └─ my_weight_pack/
      └─ inventory_weight/
         └─ items/
            └─ item_weights.json

Example pack.mcmeta:

{
  "pack": {
    "pack_format": 15,
    "description": "Custom MT Inventory Weight item weights"
  }
}

Example item_weights.json:

{
  "minecraft:iron_ingot": 100.0,
  "minecraft:diamond": 200.0,
  "minecraft:obsidian": 1200.0
}

Old Config Migration

Old versions used item-specific config files such as:

config/inventoryweight/inventory_weights_items.json

Some experimental or transitional builds may also have used item-specific TOML-style config files.

WARNING

These old item-specific config files are no longer read by MT Inventory Weight.

The item weight system is now data-driven. Specific item weights must be defined through datapacks in:

data/<namespace>/inventory_weight/items/*.json

To migrate old custom item weights, move them into a datapack item weight file.