The UDC Master Reference File (MRF) is the name of the database that contains the UDC schedules together with records needed for administration, maintenance and archiving. The same name is used for the export from this database. UDC MRF contains the definitive, authorized version of the UDC and is maintained as a working tool for the UDC Consortium. The UDCC created and maintains the MRF database in order to manage the content of the UDC, to determine the need and priority for revisions, and to keep track of changes over time.

The MRF is the definitive source on which publishers base their UDC publications or services. Users other than publishers can also benefit from direct access to the MRF, whether for classification, research or other purposes. They may need to support their specific use, in particular, by employing a suitable software application.

The Master Reference File is maintained at the UDC Consortium Headquarters in the Royal Library at The Hague. It is updated once a year during December/January to incorporate revisions and amendments published in Extensions and Corrections to the UDC. English is the working language of the Consortium and the otuput from the MRF is distributed in English.