Get MARC 21 data

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Use our free service to get the British Library's catalogue records or the British National Bibliography in MARC 21.

Our free MARC 21 Service is used in more than 120 countries. Users include school and public libraries, universities, researchers.

Users are required to register for the service and agree that any usage will be strictly for non-commercial purposes, such as:

  • Resource discovery
  • Learning, teaching, academic and scientific research or private study
  • Cataloguing or acquisition
  • Provision of information solely about the registered library’s holdings for inclusion in a union catalogue or library inter-lending database
  • Verification of bibliographic information and/or identification of materials for order via interlibrary loan, from document vendors or from other sources from which materials identified may be purchased or otherwise acquired

Please see the full terms and conditions - if you can agree to these, contact metadata@bl.uk to confirm that you accept them. We will then register you and send out connection details along with a username and password.

How to access and configure the Z39.50 databases

In order to access our Z39.50 databases you will need to use a Z39.50 client. These are incorporated in commercial Library Management Systems, or you can choose to install a standalone client such as:

If you just need to access our catalogues online, please see a list of available catalogues.

Basic configuration settings

In order to access the free authenticated MARC 21 service, ensure your client uses the following configuration details:

  • Domain Name: z3950cat.bl.uk
  • Port Number: 9909
  • Database Names: ZBLACU or BNB03U
  • Record Format: MARC 21
  • Character Encoding: Unicode (UTF-8)
  • Element Set Name: F (Full) or B (Brief)

Z39.50 Attributes

The following attributes from the BIB-1 semantics are supported by our MARC 21 server:

USE (1)
Word Searching Use Value
Personal name 1
Title 4
Series title 5
ISBN 7
ISSN 8
British National Bibliography number (only on BNB03U) 10
Local control number 12
DDC (Dewey Decimal Classification) 13
Subject heading (other) 21
LCSH (Library of Congress Subject Heading) 27
Date 30
Date of publication 31
British National Bibliography number (only on BNB03U) 48
Place of publication 59
Author 1003
Author name personal 1004
Any 1016
Server choice 1017
Publisher 1018
ISMN (International Standard Music Number) 1092
Browse Searching Use Value
Personal name 1
Title 4
Series title 5
ISBN 7
ISSN 8
British National Bibliography number (only on BNB03U) 10
Local control number 12
DDC (Dewey Decimal Classification) 13
Subject heading (other) 21
LCSH (Library of Congress Subject Heading) 27
British National Bibliography number (only on BNB03U) 48
Place of publication 59
Author 1003
Author name personal 1004
Publisher 1018
ISMN (International Standard Music Number) 1092
Sorting Use Value
Personal name 1
Title 4
Date 30
Date of publication 31
Author 1003
Relation (2) 3 (equal)
Position (3) 

1 (first in field), 
3 (any position in field)
Structure (4) 1 (phrase), 2 (word), 6 (word list)
Truncation (5)

1 (right truncation), 2 (left truncation), 
100 (do not truncate)
Completeness (6) 

1 (incomplete sub-field), 
3 (complete field)