Overview of UDC Online

UDC Online is a hub of UDC schemes in multiple languages based on a collaboration between the UDC Consortium and UDC publishers in several countries. Since January 2013 UDC schedules in English have been published by the UDC Consortium (The Hague).


The English UDC Online is a complete standard edition of the scheme on the Web containing more than 70,000 classes extended with over 11,000 records of historical UDC data (cancelled numbers). This online tool offers a number of functions to facilitate searching, browsing, parsing, validating, filing and building of UDC numbers. Searching and viewing of historical data is intended to help users in tracing cancelled numbers and their redirections that may still exist in library collections.

Who should use UDC Online?

UDC Online is a professional indexing and classification tool intended for UDC specialists in libraries and other bibliographic and information services. It is a UDC reference tool and is independent of any local indexing policies and principles that may guide the application of UDC. Although this is a user friendly tool, with many notes and instructions assisting indexers, it assumes that users are professionals familiar with UDC and document content indexing.


The system is driven by the UDC Master Reference File database, maintained in English and regularly updated by the UDC editorial team at their headquarters in The Hague. The UDC Online is updated biannually following changes published in the Extensions and Corrections to the UDC and released in the subsequent version of the UDC Master Reference File (UDC MRF).

Ownership and maintenance

The system is created, maintained and run by the UDC Consortium in The Hague, who owns the copyright on the UDC Content and its versions in English language. This has many advantages for users as they will be supported by a team of UDC specialists working on UDC content and maintaining the UDC database.

User support

User support for English is provided by the UDC Editorial Team.

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