LDtk files contain 3 types of unique identifiers:

String identifiers

These are the ones displayed in the editor, editable by the user. They follow some constraints:

• only letters, numbers and underscores,
• no space, nor any special character,
• they are Capitalized by default, but you can change this behavior from the Project Settings panel.

Integer UIDs

Each definition has a uid field which stands for Uniquer Identifier.

Each instance of whatever (entities, layers etc.) also has a defUid field which simply refers to the corresponding definition with the same uid.

Instance identifiers IID

Coming soon

Future deprecation of integer UIDs

The long term plan is to get rid at some point of the current integer UID system, to replace it with the much more robust UUID system used by instance identifiers.