Click here to skip to content

The British Library, MARC 21 and UKMARC

Support for British National Bibliography (BNB) data in UKMARC format ceased on 31 December 2008; BNB data is now only available in MARC 21 format. Please read below for details about conversion help.

The British Library adopted MARC 21 as its cataloguing format in June 2004 as part of the implementation of an integrated library system. MARC 21 is an international format used by other national libraries and the wider bibliographic community. Records are now created in MARC 21 for resource discovery and for distribution via its Exchange file services.

The Library's move to MARC 21 is part of a general movement by libraries in the UK and elsewhere from UKMARC, the former national format, to MARC 21. To support remaining UKMARC users, the Library undertook to maintain UKMARC and related Exchange file services for up to three years while users made arrangements to convert their library systems to MARC 21. This period has now come to an end and support for British National Bibliography (BNB) data in UKMARC ceased on 31 December 2008.

UKMARC support for other products ceased with effect from 31 December 2007, unless individual arrangements had been agreed with the British Library. There will be no further development of the UKMARC format and services.

For assistance in converting from UKMARC to MARC 21, the following tools are available:

  • Conversion tables covering all the UKMARC fields and content designation used in monograph and serial records in the British National Bibliography (BNB). The tables detail how each field and subfield should be converted. They are available for download here (Zip file 491KB).


  • USEMARCON, the software application that allows users to convert bibliographic records from one MARC format to another. This is made available as unsupported freeware. For further details, please see our webpage.

The Library is aware that, for a transitional period, some of our users may require assistance in converting from MARC 21 to UKMARC. We have therefore decided to share the rules file that the Library developed for use with the software USEMARCON. This is made available with the following caveats: the rules have been written for monographs and serials only; they only include fields present in BNB records. The rules and associated files are provided unsupported and free of charge. They are available for download here (Zip file 26KB).

MARC 21 Documentation is available on the Library of Congress website:


For further information please contact:

The British Library
Collection Metadata
Boston Spa, Wetherby
West Yorkshire
LS23 7BQ
United Kingdom

Email: metadata@bl.uk