About the LC Catalog
Use Z39.50/SRW/SRU Services for Metadata Retrieval
For seamless access to LC Catalog metadata, the Library recommends using our Z39.50/SRW/SRU services instead of screen scraping LC Catalog record displays. Configuration information for Z39.50/SRW/SRU services to LC catalogs is available at: LC Z39.50/SRW/SRU Server Configuration Guidelines
Scope of the Catalog
Library of Congress collections contain over 171 million books, periodicals, manuscripts, maps, music, recordings, images, and electronic resources. The LC Catalog contains over 20 million records describing these collections. You can search catalog records by keyword or browse by authors/creators, subjects, names/titles, series/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 LC Catalog includes many early records (primarily for books and periodicals) created by the Library between 1898 and 1980. These records are gradually being updated to reflect contemporary language and usage. Authors/creators 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 or archival collections rather than individually identifying each specific item, with records for many archival collections linked to more detailed guides available in Finding Aids Search. Some Library special format materials are also discoverable via separate expert search systems (such as Chronicling America and the Prints and Photographs Online Catalog) that supplement search available from Library of Congress Home. Some records for digitized items may only be found on the Library's Digital Collections website. Databases, ejournals, and ebooks that are available to patrons onsite (including items found in fee-based online services) can be located through the E-Resources Online Catalog. Primo opens in a new window, a web-scale discovery service, offers access to articles, ebooks, and other eresources in selected subscription and free resources available at LC. For more information, see What other catalogs are available?
LC Catalog Interface
The LC Catalog interface incorporates responsive web design principles that enable optimal viewing and interaction across a wide range of devices and platforms, with the Library's Ask a Librarian service presented prominently on every page. The LC Catalog interface remains committed to:
Make the LC Catalog Accessible to All
Responsive design is inherently accessible, ensuring that the LC Catalog supports the Library's mission to make its resources available to Congress and the American public. Responsive design provides easy reading and navigation with a minimum of resizing, panning, and scrolling, regardless of the size of the device, from desktop computer monitors to mobile phones, tablets, etc. The LC Catalog meets the requirements of the Americans with Disabilities Act (ADA) and remains accessible to all patrons including those with disabilities. Library experts in assistive technology test the catalog design with screen readers such as JAWS opens in a new window to make sure patrons who prefer these assistive tools have full access to catalog functionality.
Remain Flexibile in Design to Enable New Functionality
Flexible design of the LC Catalog enables the Library to efficiently expand functionality and provide better information security for patrons requesting materials from Library collections.The catalog supports OpenURLs — URLs that dynamically construct web searches for full text available either onsite at the Library or through fee-based and freely-accessible websites. When you are onsite at the Library, click the Find It button to locate full text content accessible from Library reading rooms. To help offsite patrons, records in the LC Catalog embed "invisible" snippets of HTML code (called COInS) that enable browser plug-ins and reference citation software to build OpenURLs that link to eresources available from local institutions.
Implement the Library of Congress Web Standards
The LC Catalog's responsive interface reflects the Library's web standards, presenting patrons with a more consistent experience across the Library's website.
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 a Reader Registration Station, located in the Madison Building, Room LM 133 (in the Newspaper & Current Periodicals Reading Room) or the Jefferson Building, Room LJ 139 (in the Microform and Electronic Resources Center).
Patron Account Benefits
Registered readers — as well as Congressional and Library staff with Library of Congress patron accounts — may request materials online through the LC Catalog using their individual "account numbers." See the Guide for Requesting Materials in the Library's Catalog for additional information.
- In Primo: patrons can create a personal account that allows you to save items, searches, and personalization choices across search sessions.
- In the HathiTrust Digital Library: patrons can download full PDFs of public domain works that appear in HathiTrust (note that logging on to HathiTrust does not provide access to page images of "Limited (search only)" items). Patrons can also access HathiTrust's Collection Builder opens in a new window, a tool that facilitates the creation and sharing of personal collections of HathiTrust items for private or public use. Click here for more information on logging in to HathiTrust.
Library Holdings and Availability Information
Records in the LC 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 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.
Information from the Library's name and subject authority records is integrated into LC 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 Catalog search results sets for further manipulation, you may develop more precise search strategies using Advanced Search and the EXPERT option on Keyword Search. These search forms support Boolean operators and nesting; Keyword (EXPERT) also enables you to enter more specific index codes. In addition, the Constructing Canned Search Links help page shows you how to build canned searches into the LC Catalog.
Each record in the LC Catalog can be referenced with a Permalink, displayed on individual record displays. For records assigned an LCCN, this URL identifier is an LCCN Permalink; records without an LCCN base their Permalink on the LC Catalog system identifier.
The LC Catalog complies with the Library of Congress web accessibility guidelines as well as international accessibility and industry standards:
- W3C Web Content Accessibility Guidelines 1.0, level A (See https://www.w3.org/TR/WAI-WEBCONTENT/ opens in a new window)
- Section 508 of the Rehabilitation Act (29 U.S.C. 794d) (See https://www.section508.gov/ opens in a new window)
If you have questions or comments on LC Catalog accessibility issues, please contact Collection Discovery and Metadata Services.
Special Notes for Libraries and Librarians
Librarians using the LC Catalog should note that:
- Name and subject authority records cannot be directly searched or retrieved in the LC Catalog. To search authority records directly, please go to LC Authorities at https://authorities.loc.gov. LC's Linked Data Service at id.loc.gov also makes commonly used Library vocabularies available in RDF and other semantic-oriented formats.
- It is not possible to store search results sets for further manipulation in the LC 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 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 Catalog search queries in either text or MARC 21 (MARC UTF-8 or MARC-8) formats. Links on individual record displays also enable records with LCCNs to be downloaded in MARCXML or MODS formats. In addition, records can be exported using Z39.50/SRU by configuring your Z39.50/SRU client according to the LC's technical guidelines. Z39.50/SRU exports can be formatted in MARC-8, MARC UTF-8, MARCXML, MODS, or Dublin Core.
- Number searches by LCCN, ISBN, ISSN, and ISMN are available from Browse, Advanced Search, and Keyword Search.
- The LC 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 LC Catalog.
- Institutions interested in requesting materials should consult the Library's Interlibrary Loan policy.