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Version: 1.20.x

Slot Types

A tutorial on how to register and modify slot types that are recognized by Curios.


The recommended way to register a slot type is through a datapack. If a user or developer is unfamiliar with datapacks, it is recommended to read through the wiki page in order to understand the concept and structure before proceeding to the rest of this page.

Alternatively, users can instead choose to use the Curios configuration to create and modify slot types. There are fewer features than those offered in the datapack method, but some users may find the process to be more straightforward.

If using one of the Preset Slot Types, this step can be skipped since Curios natively provides the needed datapack registration.


Why are my registered slot types not appearing?

Registering slot types makes them available for use; however, they are not added to any entities (including players) by default. In order to add them to an entity, please refer to the next step on adding slot types to entities.


The file should be a .json file with the identifier for the slot type to be registered as the name. This file should be located in the ~/data/(namespace)/curios/slots/ folder of the datapack.

Example: Registering a head slot type requires creating a head.json file located in ~/data/(namespace)/curios/slots/ so the final path should look like ~/data/(namespace)/curios/slots/head.json.


The (namespace) field should be replaced by the namespace chosen for this portion of the datapack. If this is a part of a mod, the namespace is usually the mod ID. If this is part of a user-defined datapack, then the namespace can be anything that is lowercased with no special characters.


The structure of the .json file for the slot type consists of a top-level JSON object that holds various fields related to that slot type.

All fields are optional unless otherwise noted. Each field denotes certain merging behavior which defines how the field is merged between all data files that include it.

replace (boolean)

When true, replaces data from lower-priority datapacks.

  • default: false
  • merging: N/A

size (integer)

The number of slots of this slot type to give by default.

  • default: 1
  • merging: The highest size will be used.

operation ("SET"|"ADD"|"REMOVE")

Whether to use size to set, add, or remove from the total number of slots.

  • default: "SET"
  • merging: N/A

order (integer)

The order the slots will appear in the native Curios GUI, lower numbers appear first.

  • default: 1000
  • merging: The lowest order will be used.

icon (string)

The location of the icon to use for the slot type.

  • default: "curios:slot/empty_curios_slot"
  • merging: The last icon will be used.

add_cosmetic (boolean)

The location of the icon to use for the slot type.

  • default: false
  • merging: true if any data file sets this field to true.

use_native_gui (boolean)

When false, does not add the slot type to the native Curios GUI.

  • default: true
  • merging: false if any data file sets this field to false.

render_toggle (boolean)

When false, does not allow the slot type to toggle its rendering.

  • default: true
  • merging: false if any data file sets this field to false.


Whether to drop, keep, destroy, or follow the keepCurios configuration setting.

  • default: "DEFAULT"
  • merging: N/A

validators (string[])

The list of registered predicates from the Curios API used by this slot type to validate item insertions. For more information about validators, please see the page on slot assignments.

  • default: ["curios:tag"]
  • merging: Each entry is added into the final array.

Which operation value should I use?

In most cases, "SET" (also the default if no value is defined) will accomplish the desired result. It denotes that a slot type should have a certain amount of slots by default, with the highest value among all consumers being used. "ADD"and "REMOVE" are inherent slot modifiers and are based on the amount of slots specified by all "SET" operations, the result of which can change based on the mods/datapacks loaded.


"order": 20,
"size": 4,
"icon": "curios:slot/empty_custom_slot",
"add_cosmetic": true

This slot type will have a relatively low order of 20, which will make it appear higher than most slots. It also has size of 4 which means that it will register 4 slots to any given entity by default. For the GUI, it uses an icon located at curios:slot/empty_custom_slot. It also has added a cosmetic slot so there will be an additional slot for cosmetic items next to it in the Curios GUI.

Modifying a Slot Type

The process of modifying a slot type is identical to registering a new slot type, except using the same identifier as the existing slot type. All slot types that share an identifier will be merged according to the Merge Behavior of each field as outlined above.


Curios natively provides data for the ring slot, which defaults the size to 1. In order to increase the size to 2, create a ring.json slot registration file in the datapack with the contents:

"size": 2

This will merge the size data of this registration with the existing registration provided by Curios, keeping all of the other data intact while increasing the number of slots to 2.