The root of a metadata file is a key-value map. LOOT will recognise the following keys, none of which are required. Other keys may also be present, but are not processed by LOOT.
The prelude can have any value, but if a masterlist prelude path is provided when loading metadata, the masterlist's ``prelude`` value will be replaced by the parsed content of the masterlist prelude file. The prelude exists so that metadata that is common across different masterlists can be shared without duplication.
Note that prelude replacement is only supported when using YAML's block style and an unquoted ``prelude`` key that is not preceded by a mapping key indicator and that is immediately followed by a colon separator, i.e. ``prelude:``.
The plugin data structures that hold all the plugin metadata within the file. It is a mixture of a list and a set because **no non-regex plugin value may be equal to any other non-regex plugin value** , but there may be any number of equal regex plugin values, and non-regex plugin values may be equal to regex plugin values. If multiple plugin values match a single plugin, their metadata is merged in the order the values are listed, and as defined in :ref:`plugin-merging`.