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Top > About Us > Functions


Acquisition and preservation of library materials

The National Diet Library (NDL), as a national library, acquires, preserves and provides Japanese publications which are the nation's cultural and intellectual assets. The acquisition of library materials is mostly based on the Legal Deposit System, while publications published before the Legal Deposit System came into force, rare and old materials, manuscripts and foreign publications are collected through purchase, donation, etc. The acquisition of Japanese and foreign materials is conducted in accordance with a policy for acquisition of materials.

Legal Deposit System

The National Diet Library Law requires that all publications published in Japan are deposited with the NDL. Through the Legal Deposit System, the NDL broadly collects publications including maps, audio materials, microfilms and CD-ROMs published in Japan. National government agencies, local public bodies and independent administrative corporations deliver a prescribed number of copies of their publications, while private publishers send one.


The NDL purchases extra copies of frequently used materials (books, magazines and newspapers published in Japan). Foreign materials and rare and old materials, which are selected in accordance with a policy for acquisition of materials, are also purchased.

Exchange and donation

Through international exchange with national libraries all over the world, the NDL makes efforts to acquire publications of foreign governments. In addition, many international organizations, including the United Nations, designate the NDL as a depository library and deposit their publications with the NDL. Donations from individuals and groups are also accepted.


The NDL has a duty to conduct appropriate management and to preserve library materials as the cultural heritage of the nation and to assure future access to them.
The NDL is engaged in preventing deterioration by various methods such as media conversion including digitization, restoration of damaged originals as well as disaster prevention, maintenance of stack environment and training programs on preservation, and spreading this information. The NDL has also been testing various methods of preserving digital resources.

Acquisition of Internet information and online publications

The NDL exhaustively collects Internet information put out by public institutions and private online publications (e-books and e-magazines). (Charge-free private online publications without Digital Rights Management (DRM) are under this obligation at the moment.)
Collected websites are available in WARP, while online publications are available in the National Diet Library Digital Collections. Private online publications are provided only inside the library facilities.

Compilation and provision of catalogs, bibliographies and indexes

The NDL compiles and provides various bibliographies of library materials. Most of the collections are searchable through the NDL-OPAC and NDL Search on the website.

Providing National Bibliography

The NDL provides accurate bibliographic information on the newly collected publications published in Japan and Japanese-language materials published in foreign countries, through NDL-OPAC. Data can be downloaded in the MARC format and in-process bibliographical data is also provided. In addition, they are distributed as JAPAN/MARC (machine-readable version of the national bibliography).

Japanese Periodicals Index

Index for searching articles carried in major Japanese periodicals, approximately 21,000 titles of which 11,000 titles are still published. The NDL provides data which have been accumulated since 1948, on the NDL-OPAC, etc.

Index Database to Japanese Laws, Regulations and Bills

An online database providing information on the history of Japanese current or abolished laws since 1867. Users can also refer to minutes of the Diet at the stage of deliberation. This is available on the NDL website.

Interlibrary cooperation

Domestic cooperation

The NDL responds to many requests for loan, copy and reference from other domestic libraries. The NDL introduces trends and topics of libraries and library and information science inside and outside Japan through its information bulletin “Current Awareness” and the website “Current Awareness Portal” (mostly in Japanese).

Providing infrastructure for interlibrary cooperation

The NDL carries out research on library and information science and provides various training programs for librarians. It manages the “NDL National Union Catalog Network System” (in Japanese), a union catalog of Japanese books, as well as providing functions to support interlibrary loan between libraries participating in this network system. It also compiles national union catalogs of newspapers, braille and recorded books and children's literature, which are provided in the NDL Search. The NDL also collects data for people with visual disabilities (e.g. audio data in DAISY format, braille data) made by public libraries. The collected data are transmitted to individuals with visual disabilities or libraries via data transmitting services.
In addition, it conducts the “Collaborative Reference Database Project” (in Japanese), which collects and accumulates data of reference cases from the member libraries and provides them on the Internet, as well as allocating the International Standard Identifier for Libraries and Related Organizations (ISIL) to libraries in Japan and maintaining it.

International cooperation

As the sole national library in Japan, the NDL engages in a wide variety of cooperation activities such as library services and mutual visit programs with overseas libraries. It also acts as the Japanese center for the International Standard Serial Number (ISSN) Network and as the Regional Center for Asia for the IFLA Strategic Programme on Preservation and Conservation (IFLA/PAC).

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