AddTag will apply a tag to an Instance, doing nothing if the tag is already applied to the instance. Successfully adding a tag will fire a signal created by CollectionService:GetInstanceAddedSignal() with the given tag.

Warning: When tagging an instance, it is common that some resources are used to give the tag its functionality, e.g. event connections or tables. To prevent memory leaks, it is a good idea to clean these up (disconnect, set to nil, etc) when no longer needed for a tag. Do this when calling CollectionService:RemoveTag(), calling Instance:Destroy() or in a function connected to a signal returned by CollectionService:GetInstanceRemovedSignal().

GetInstanceAdded is given a tag (a string) and returns a signal which fires under two conditions:

• The tag is assigned to an instance within the DataModel (game) using CollectionService:AddTag() or Instance:AddTag().
• An instance with the given tag is added as a descendant of the DataModel, e.g. by setting Instance.Parent or similar.

Subsequent calls to this method with the same tag return the same signal object. Consider also calling CollectionService:GetTagged() to get a list of objects that already have a tag (and thus won't fire the event if they already are in the DataModel).

See also CollectionService:GetInstanceRemovedSignal(), which returns an event that fires under similar conditions.

GetInstanceRemoved is given a tag (a string) and returns a signal which fires under two conditions:

• The tag is removed from an instance within the DataModel (game) using CollectionService:RemoveTag() or Instance:RemoveTag().
• An instance with the given tag is removed as a descendant of the DataModel, e.g. by un-setting Instance.Parent or similar.

Subsequent calls to this method with the same tag return the same signal object. The signal is useful for cleaning up resources used by objects that once had tags, such as disconnecting connections.

See also CollectionService:GetInstanceAddedSignal(), which returns an event that fires under similar conditions.

GetTagged returns an array of objects with a given tag which are descendants of the DataModel (game). Such tags have been added using CollectionService:AddTag(), and removing a tag using CollectionService:RemoveTag() will ensure this method does not return them. Although the name of this method is past-tense, this method only returns objects presently tagged with the given tag. It will not return objects that once had a tag but no longer have it.

If you want to detect all objects with a tag, both present and future, use this method to iterate over objects while also making a connection to a signal returned by CollectionService.GetInstanceAddedSignal.

This method does not guarantee any ordering of the returned objects. Additionally, it is possible that objects can have the given tag assigned to them, but not be a descendant of the DataModel, i.e. its parent is nil. This method will not return such objects.

GetTags is given an instance and returns an array of strings, which are the tags applied to the given object.

local CollectionService = game:GetService("CollectionService")
local object = workspace.Model
local tags = CollectionService:GetTags(object)
print("The object " .. object:GetFullName() .. " has tags: " .. table.concat(tags, ", "))

This method is useful when you want to do something with multiple tags at once on an object. However, it would be inefficient to use this method to check for the existence of a single tag. For this, use CollectionService:HasTag() to check for a single tag.

HasTag returns whether a given object has a tag.

• Using CollectionService:AddTag() to add the tag will cause this method to return true.
• Using CollectionService:RemoveTag() to remove the tag will cause this method to return false.

By extension, any tags returned by a call to CollectionService:GetTags() on an object will return true when used with this method.

RemoveTag will remove a tag from an instance. This method will not throw an error if the object did not have the tag in the first place. Successfully removing a tag will fire a signal created by CollectionService:GetInstanceRemovedSignal() with the given tag.

When removing a tag, it is common that some resources are used to give the tag its functionality, e.g. event connections or tables. To prevent memory leaks, it is a good idea to clean these up (disconnect, set to nil, etc) when no longer needed for a tag.

This event fires when a tag is added to an object and the added tag is the only occurrence of that tag in the place.

This event fires when a tag is removed from an object and the removed tag is no longer used anywhere in the place.