Weight datapacks

Weight datapacks let you change item weights for a world. Install them on the server, or in the world folder for singleplayer. Players receive the resulting weights automatically.

Heavy Inventories includes default weights. A datapack can replace a few of them without supplying a full catalog.

Change an item weight

Use a datapack with valid pack.mcmeta metadata for Minecraft 26.3. Weight files go inside its data folder, alongside any recipes or other data the pack supplies.

1. Find the item’s ID. Enable advanced tooltips with F3+H, then hover over it.
2. Split the ID at the colon. The part before it is the namespace; the part after it is the item path.
3. Create a JSON file at data/<namespace>/heavyinventories/weights/<item path>.json.
4. Give the file a JSON object with exactly one field, as described below.

For minecraft:feather, the file is data/minecraft/heavyinventories/weights/feather.json. Use the item’s namespace, even if your datapack has a different name. For blocks, use the inventory item’s ID.

Choose one field per file. Do not combine them or add extra fields. Weight values must be numbers, not quoted text. Zero makes the empty item weightless; a container’s contents still count. Negative values are not accepted.

Install and check the pack

1. Put the pack folder or ZIP into the world’s datapacks folder. Its pack.mcmeta and data folder must be at the pack root, without an extra enclosing folder.
2. Run Minecraft’s /reload as an operator.
3. Use /datapack list enabled to check that the pack is active. If it isn’t, find it with /datapack list available and enable it using /datapack enable and command completion.
4. Check an item’s tooltip. For a fuller check, run /heavyinventories dump minecraft, or replace minecraft with the mod’s namespace.

After later edits, run /reload again. Connected players receive the updated weights without reconnecting.

Pack priority

If two packs supply a file for the same item, the higher-priority pack wins. The whole file is replaced; fields aren’t merged.

Enable your override pack last when it should take precedence. If an edit doesn’t appear, check the enabled pack order and the source recorded in a weight report.

Removing your override reveals the next available definition, including bundled defaults. To replace a fixed default with recipe calculation, use an infer definition instead.

Recipe-derived weights

An item with no fixed weight can get its weight from a supported recipe. Ingredient weights are added together and divided by the number of output items. If several usable recipes or ingredient choices exist, the lowest calculated weight is used.

For example, if a log weighs 8 pounds and a recipe makes four planks, that recipe gives each plank a weight of 2 pounds. A fixed plank weight would take precedence.

Supported recipes include ordinary shaped and shapeless crafting, smelting, blasting, smoking, campfire cooking, and stonecutting with fixed outputs. Recipes that leave crafting remainders, produce component-dependent results, or use unsupported custom behavior need explicit weights.

If no fixed or usable recipe-derived weight is available, the item gets 0.1 pounds. Set explicit weights for raw materials and items whose recipes don’t provide a useful result. Use infer on an already-defined item when you want recipe changes to affect it.

Errors and optional mods

A definition for an item from an absent mod is ignored with a warning. You can include optional mod weights in the same pack.

Malformed weight files reject the weight update. An existing world session keeps its previous weight table. Check the server log for the file and error, correct it, then run /reload again.