The Format Library serves as a knowledge base for all of the information regarding the different formats that are stored by Rosetta. This knowledge base allows users to manage their repositories and plan Preservation-related activities. It allows users to associate risks and metadata extraction tools with the different formats defined in PRONOM and other registries.

The Format Library uses a master copy that is maintained by one or more Rosetta Preservation Managers, who update the library collectively as needed and distribute it to all libraries through an export task. All other Rosetta libraries can import the latest Format Library version on an as-needed bases, and they can customize their version and maintain customizations during updates.

The Local Format Library is based on the Global Format Library. The local version includes all of the formats, risks, and so forth of the global version, but local users can make institution-based changes and adjustments to those components that only impact their local library.