Miscellaneous Details

String Encoding

  • All output strings are encoded in UTF-8.

  • Metadata files are written encoded in UTF-8.

  • Input strings are expected to be encoded in UTF-8.

  • Metadata files read are expected to be encoded in UTF-8.

  • File paths are case-sensitive if and only if the underlying file system is case-sensitive.

Language Codes

All language strings in the API are codes of the form ll or ll_CC, where ll is an ISO 639-1 language code and CC is an ISO 3166 country code. For example, the default language for metadata message content is English, identified by the code en, and Brazilian Portuguese is pt_BR.


All errors encountered are thrown as exceptions that inherit from std::exception.

Metadata Files

LOOT stores plugin metadata in YAML files. It distinguishes between three types of metadata file:

  • masterlist files: each game has a single masterlist, which is a public, curated metadata store

  • masterlist prelude files: there is a single masterlist prelude, which is a public store of common metadata templates that can be shared across all masterlists

  • userlist files: each game has a userlist, which is a private user-specific metadata store containing metadata added by the LOOT user.

All three files use the same syntax, but the masterlist prelude file is used to replace part of a masterlist file before it is parsed, and metadata in the userlist extends or replaces metadata sourced from the masterlist.

LOOT’s plugin metadata can be conditional, eg. a plugin may require a patch only if another plugin is also present. The API’s loot::DatabaseInterface::LoadLists() method parses metadata files into memory, but does not evaluate these conditions, so the loaded metadata may contain metadata that is invalid for the installed game that the loot::DatabaseInterface object being operated on was created for.


All unevaluated metadata is cached between calls to loot::DatabaseInterface::LoadLists().

The results of evaluating metadata conditions are cached between calls to loot::GameInterface::LoadPlugins(), loot::GameInterface::SortPlugins() and loot::DatabaseInterface::GetGeneralMessages().

Plugin content is cached between calls to loot::GameInterface::LoadPlugins() and loot::GameInterface::SortPlugins().

Load order is cached between calls to loot::GameInterface::LoadCurrentLoadOrderState().


The following may involve filesystem access and reading/parsing or writing of data from the filesystem:

Evaluating conditions may also involve filesystem read access.

loot::GameInterface::SortPlugins() is expensive, as it involves loading all the content of all the plugins, apart from the game’s main master file, which is skipped as an optimisation (it doesn’t depend on anything else and is much bigger than any other plugin, so is unnecessary and slow to load).

loot::DatabaseInterface::GetGroupsPath() involves building a graph of all defined groups and then using it to search for the shortest path between the two given groups, which may be relatively slow given a sufficiently large and/or complex set of group definitions.

All other API functions should be relatively fast.