In 1971, the National Diet Library started compiling catalogs and indexes using computers. At that time the NDL provided online information services to the Diet, and to the prefectural and other libraries, through public communications lines. In 1997 when the NDL website was opened, bibliographical information on Japanese books was partly made available through the Internet. In 2000, the NDL site enabled search of Japanese books acquired from 1948 and Western books from 1986.
In 2002, the NDL opened an online accessed public catalog (NDL-OPAC) through which the holdings data of the Library such as Japanese books published since 1868, periodicals, newspapers, and the Japanese Periodical Index (since 1948) became searchable. Since then, data of more material types, including Japanese old materials up to the Edo Period, have been added and now most of the collection is searchable on the NDL-OPAC.
Registered users can request copies through the online catalog (NDL-OPAC) and copies are sent by mail (Japanese version only).

In recent years information technology has penetrated into many corners of society, increasing remarkably the importance of electronic information. As a result it has become possible to transmit primary information (i.e., texts) in addition to secondary information (catalogs, indexes, etc.) to the public at large through the Internet and other communications networks.
The NDL website provides such primary information as Full-text Database of the Minutes of the Diet, Digitized Contents, Digital Library from the Meiji Era, Web Archiving Project and Online Gallery.

Any person 18 years of age and over is qualified to use the services of the National Diet Library. Except for some of its special materials rooms, the NDL applies a closed stack system for its materials. There are a total of 15 reading and special materials rooms in the Main Building and Annex.
The materials may be read or photocopied inside the library. Although individuals are not allowed to take materials out on loan from the library, the NDL does provide interlibrary loan service to public, university and specialized libraries. Taking advantage of interlibrary loan services, it is possible to read NDL materials without visiting the NDL.
The National Diet Library has exterior and interior facilities specially designed to assist the visit of persons with disabilities.
*Services for the handicapped
*Library Services

An important mission of the National Diet Library is to assist the legislative activities of the Diet by providing research and information services in addition to library materials.
The Research and Legislative Reference Bureau, takes charge of research and information service (see page of services for the Diet), carries out wide-ranging research as political, economic and social systems of Japan and other countries making most of the library materials. The Bureau answers requests from Diet Members and Dietstaff about 45,000 times a year. Recently the number has moved into the 40,000 range.

The National Diet Library extends its services to the executive and judicial agencies of Japan chiefly through its Branch Libraries established within the government ministries and agencies and the Supreme Court. The NDL and its Branch Libraries work in concert through a communications network, with the NDL Branch Libraries and Cooperation Division assisting in the work of the Branch Libraries, managing the network system, and extending library services to the staff members of the executive and judicial agencies directly or indirectly.

As Japan's only national library, the NDL cooperates with various libraries and library associations in Japan. The NDL receives numerous requests from libraries across Japan for the interlibrary loan, photoduplication service and reference service which they could not meet by themselves.

Moreover, as the national library of Japan, the NDL cooperates with libraries throughout the world. Among its multifaceted cooperation activities are the exchange of government and private publications, interlibrary loan, photoduplication service, reference service and exchange of bibliographic data.
The NDL also serves as the Japan center for the ISSN(International Standard Serial Number) Network and as the Asian regional center for the IFLA PAC (International Federation of Library Associations' Core Activity for Preservation and Conservation).
In FY 2007, the NDL provided 30,441 items and answered 7,784 reference questions for libraries of Japan and all over the world.

Since 1975, the National Diet Library has been producing tape-recorded versions of academic writings from its stock and providing them by loan service through local libraries throughout Japan. Further, the NDL publishes a series of "National Catalog of Braille and Tape-recorded Books" in CD-ROM form. A "Prompt Report on Braille Books and Tape-recorded Books in Japan (in Japanese)" is made available on the NDL website, while efforts are continuing to collect publications in raised letters and large letters for the visually handicapped.