UK National Agency for the ISIL
The International Standard Identifier for Libraries and related organizations.
The ISIL is the International Standard Identifier  that can be assigned to a library or related organization. An ISIL can also be assigned to sub-units of an organization.
In 2007 the British Library became the UK National Agency for the assignment of the ISIL to organizations in the United Kingdom, Crown Dependencies and Overseas Territories.
The British Library is not responsible for the assignment of ISILs to libraries and related organizations in the Republic of Ireland.
ISILs assigned to libraries by the British Library are based on MARC organisation codes which are made globally unique by the addition of a country code prefix (ISO 3166-1).
How to obtain an ISIL
- Check your organisation does not already have an ISIL by searching the:
Directory of ISILs for UK organisations
(PDF format 313 KB)
The directory was last updated on 23 March 2015.
- Please fill in this form (Word format 29KB) and email it to firstname.lastname@example.org to request a code.
Requests for an ISIL for one organization will be processed within a few days.
If you require codes for more than one organization, or for multiple sub-units of one organization, this processing will take longer depending on the overall number and will be assessed on a case-by-case basis. Please contact us at the above e-mail address to discuss.
We make every effort to fulfil requests as promptly as possible; please help us by requesting your ISIL in good time.
ISILs are 16-character variable length codes which uniquely identify libraries and related organizations in an international context. They can accommodate existing national library identification systems.
The Danish National Library Authority is the International Authority for the registration and maintenance of the standard. Its role is to maintain a source of information about the National Agencies involved and to supervise the use of country and non-country prefixes. It also has a promotional role.
More details about the ISIL are available from the ISIL Registration Authority.
 ISO 15511:2011
For further information please contact:
The British Library
Boston Spa, Wetherby
Tel: + 44 (0) 1937 546124
Fax: + 44 (0) 1937 546586