The Universal Decimal Classification (UDC) is a classification scheme for all fields of knowledge, a sophisticated indexing and retrieval tool. UDC is used in libraries and information services in over 130 countries and has been translated in over 40 languages. It is often regarded as a de facto standard in subject indexing and retrieval.

Since its creation in 1905, it has been extensively revised and developed, and has become a highly flexible and effective system for organizing bibliographic records for all kinds of information in any medium (it is well suited to multi-media information collections). It is structured in such a way that new developments and new fields of knowledge can be readily incorporated.

UDC Master Reference File, is maintained in a mutlilingual dabasae containing over 70,000. Exports of UDC MRF in various formats are distributed to publishers and users under a licence. An abridged scheme of over 2,600 classes in almost 50 languages, known as UDC Summary (http://www.udcc.org/udcsummary/php/index.php), is available for free (Creative Commons 3.0 Licence). UDC Summary is available as linked data (http://udcdata.info/).

The owner of the UDC is UDC Consortium, a not-for-profit organization, based in The Hague, established to maintain and distribute the Universal Decimal Classification and to support its use and development.

Nature of documentation: Other