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About the LC Online Catalog

Scope of the Catalog

Library of Congress collections contain over 147 million books, periodicals, manuscripts, maps, music, recordings, images, and electronic resources. More than 16 million records describing these collections are located in the LC Online Catalog. You can search these records by keyword or browse by authors/creators, subjects, name/titles, uniform titles, and call numbers. Browse lists also include searching aids such cross-references and scope notes.

Library of Congress cataloging dates back to 1898. The Online Catalog includes many early records (primarily for books and periodicals) created by the Library between 1898 and 1980. These records -- originally maintained in a separate database -- are gradually being updated to reflect contemporary language and usage. Names and subjects found on older records often contain the legend [from old catalog] to indicate possible deviations from current LC practices. In addition, records for some materials cataloged before 1980 are only available to researchers onsite in the Library's Main Card Catalog.

Items in the Library's special collections are generally described as aggregations rather than individually identifying each specific item. LC Online Catalog records for many archival collections are linked to more detailed guides searchable in the Finding Aids system. Records for the Library's still images can be found in the Prints and Photographs Online Catalog; records for portions of Library recordings can be searched in SONIC (Sound Online Inventory and Catalog). Databases, ejournals, and ebooks accessible onsite -- including items found in fee-based online services -- are linked through the E-Resources Online Catalog.

Reader Registration

Public patrons of Library reading rooms must obtain a Reader Identification Card. These cards are free-of-charge and are valid for two years from the date of issue. Patrons must present in person a valid driver's license, state-issued identification card, or passport at the Reader Registration and Researcher Guidance Office, located in the Madison Building, Room LM 140 (First Floor, near the Independence Avenue entrance <view campus map>).

Registered readers may request materials online through the LC Online Catalog using their individual "account numbers." See the Guide for Requesting Materials in the Library's Online Catalog [PDF, 176KB] (revised August 2012) for additional information.

Library Holdings and Availability Information

Records in the LC Online Catalog display holdings and availability information for items -- including their call numbers or shelf location, the Library reading room where they must be requested, and their charge status. Items stored offsite may require additional time to be delivered to the Library campus. Note as well that LC Online Catalog records may indicate the Library holds one copy of a work, even though additional copies may actually be available in the Library's collections.

Please consult reference staff if you have questions about the holdings or availability of Library materials.

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Searching Aids

Information from the Library’s name and subject authority records is integrated into LC Online Catalog Headings Browse Lists through references (See and See also terms) and scope notes. Search using Browse or click on heading links in individual record displays to see these references.

While it is not possible to store LC Online Catalog search results sets for further manipulation, you may develop more precise search strategies using Advanced Search and the Keyword (EXPERT) option on Keyword Search. These search forms support Boolean operators and nesting; Keyword (EXPERT) also enables you to enter more specific index codes.

Each record in the LC Online Catalog can be referenced with a Permalink, displayed on individual record displays. For records that contain an LCCN, this URL identifier will be an LCCN Permalink; records without an LCCN base their Permalink on the LC Online Catalog system identifier.

Accessibility

This version of the LC Online Catalog complies with the Library of Congress web accessibility guidelines as well as international accessibility and industry standards:

If you have questions or comments on LC Online Catalog accessibility issues, please contact the ILS Program Office at ils@loc.gov.

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Special Notes for Libraries and Librarians

Librarians using the LC Online Catalog should note that:

  • Name and subject authority records cannot be directly searched or retrieved in the LC Online Catalog. To search authority records directly, please go to Library of Congress Authorities at http://authorities.loc.gov/
  • It is not possible to store search results sets for further manipulation in the LC Online Catalog, although several thousand records can be saved and exported for manipulation in third-party applications.
  • The Library of Congress uses the international MARC 21 encoding standard to represent and communicate bibliographic, authority, and holdings data in LC Online Catalog records. This standard explicitly characterizes the structure, content designation, and data content (or fields) found in each Catalog record. Some data specific to the Library is contained in locally-defined MARC fields.
  • You can save one or more records from LC Online Catalog search queries in either text or MARC 21 (MARC UTF-8 or MARC-8) formats. Using links in the left panel of individual record displays, records with LCCNs are also available in MARCXML or MODS. In addition, records can be exported using Z39.50/SRU, either through the LC Online Catalog's Z39.50 Gateway or by configuring your Z39.50/SRU client according to the LC's technical guidelines.
  • Number searches by LCCN, ISBN, and ISSN are available from Browse or through number searches using the LC Online Catalog's Z39.50 Gateway.
  • The LC Online Catalog contains records for items in the Library's collections. Therefore, not all records for periodicals in CONSER (Cooperative Serials Cataloging Program) or books cataloged by the Library's Cataloging in Publication program will be found in the Online Catalog.
  • Institutions interested in requesting materials should consult the Library's Interlibrary Loan policy.

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