Tags are generalized sets of objects in the game used for grouping related things together and providing fast membership checks.
Tags are declared in your mod’s datapack. For example,
/data/<modid>/tags/blocks/foo/tagname.json will declare an
INamedTag<Block> with ID
Similarly, you may append to or override tags declared in other domains, such as Vanilla, by declaring your own JSONs.
For example, to add your own mod’s saplings to the Vanilla sapling tag, you would specify it in
/data/minecraft/tags/blocks/saplings.json, and Vanilla will merge everything into one tag at reload, if the
replace option is false.
replace is true, then all entries before the json specifying
replace will be removed.
See the Vanilla wiki for a description of the base syntax.
Forge provides two extensions on the Vanilla syntax:
- You may declare an
optionalarray of the same format as the
valuesarray, but any values listed here that are not present will not cause the tag loading to error. This has been deprecated in favor of the vanilla method of specifying optional tag values.
- You may declare a
removearray of the same format as the
valuesarray. Any values listed here will be removed from the tag. This acts as a finer grained version of the Vanilla
Block, Item, Fluid, and EntityType tags are automatically sent from the server to any remote clients on login and reload. In addition, Forge adds TileEntityType, Potion, and Enchantment tags. Function tags are not synced.
ItemTags#getAllTags will retrieve the current
ITagCollection, from which you can retrieve a
ITag object by its ID.
ITag object in hand, membership can be tested with
tag.contains(thing), or all the objects in the tag queried with
As an example:
public static final Tag<Item> myTag = new ItemTags.Wrapper(new ResourceLocation("mymod", "myitemgroup")); // In some method Item unknownItem = stack.getItem(); boolean isInGroup = unknownItem.is(myTag);
ITagCollection returned by
#getAllTags (and the
ITags within it) may expire if a reload happens.
INamedTag fields in
ItemTags avoid this by introducing a wrapper that handles this expiring.
There are several conventions that will help facilitate compatibility in the ecosystem:
- If there is a Vanilla tag that fits your block or item, add it to that tag. See the list of Vanilla tags.
- If there is a Forge tag that fits your block or item, add it to that tag. The list of tags declared by Forge can be seen on GitHub.
- If there is a group of something you feel should be shared by the community, use the
forgenamespace instead of your mod id.
- Tag naming conventions should follow Vanilla conventions. In particular, item and block groupings are plural instead of singular (e.g.
- Item tags should be sorted into subdirectories according to their type (e.g.
- For recipes, tags can be used directly in the vanilla recipe format (see below).
- For matching items in code, see the section above.
- If you are declaring a new type of item grouping, follow a couple naming conventions:
domain:type/material. When the name is a common one that all modders should adopt, use the
- For example, brass ingots should be registered under the
forge:ingots/brasstag and cobalt nuggets under the