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Frequently Asked Questions: LC Catalog (Library of Congress)

Library buildings are closed to the public until further notice. The LC Catalog is available, however, Automated Call Slip service is only available to some patrons. More.

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Frequently Asked Questions about the LC Catalog

Accessing the LC Catalog

When I try to access the LC Catalog, I get a message that "all available connections are in use?" What does that mean?

The LC Catalog receives millions of search requests each day -- and at peak times, all connections may be in use. We are aware how frustrating this is, and we are constantly monitoring the number of simultaneous users to ensure the maximum possible access. Should you encounter connection problems, here are some tips:

  • Peak usage is typically Tuesdays, Wednesdays, and Thursdays between 10am and 2pm (US Eastern Time). We suggest trying to search before or after those hours, or on Mondays, Fridays, and weekends (during off-peak hours).
  • Please be persistent and keep trying. Users are leaving the system and freeing up connections, at about the same rate that they are entering the system. Connections open up continually as users exit the system. If you continue to try several times in quick succession, you will move up in the queue and gain access more quickly.
  • An alternative text-based interface is available through the LC Catalog Z39.50 Gateway. More about the Z39.50/SRU protocol for information retrieval is available at the Z39.50 Maintenance Agency site.

Periodically a timeout dialog box appears on my screen. Can you give me more information on session timeouts?

Because the LC Catalog receives millions of search requests each day, we need to minimize the number of inactive sessions to make sure active searchers can access the Catalog. The Library, therefore, terminates your search session when you do not navigate from one page to the next at least once in five minutes.

To keep your search session active, a timeout dialog box will appear two minutes before your session will expire, giving you the opportunity to refresh the counter. When your session closes, you will lose your search history.

How do I access the LC Catalog through the Library's wireless connections?

Onsite Library patrons with personal wireless-enabled devices may access the LC Catalog through the Library's free wireless service. Wireless users at the Library have access to research materials that may be limited to onsite use or have other restrictions on further dissemination because of copyright or licensing agreements. Restrictions on the use and further dissemination of these resources are the same whether researchers are accessing them using Library computers or via the Library's WiFi connections.

Searching/Browsing the LC Catalog

I'm sure the Library has the item I am searching for, but I cannot find it in the LC Catalog. Does the Catalog list every item in the Library's collections?

The Library of Congress acquires material from all over the world in many different formats, in hundreds of languages, and in diverse subject areas. Six methods of acquisition are used: purchase, Copyright deposit, exchange, donation, the Cataloging in Publication (CIP) and Preassigned Card Number (PCN) programs, and transfer between federal government agencies.

While the Library of Congress is one of the largest libraries in the world, it does not have a copy of every item every published. The Library's permanent collections are shaped by Collection Policy Statements, with technical agricultural works acquired mainly by the National Library of Agriculture and clinical medical works by the National Library of Medicine. Note that not all items received by the Library are selected for retention in the permanent collections.

In addition, many items from the Library's special collections are not represented by individual entries in the LC Catalog. These materials are instead described as aggregations. LC Catalog records for many archival collections are also linked to more detailed guides searchable in the Finding Aids system. Records for many of the Library's still images can be found in the Prints and Photographs Online Catalog, and 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. Records for works registered with the Copyright Office after 1978 are searchable in the Copyright Catalog. Card entries for some items cataloged before 1980 are only available to researchers onsite in the Library's Main Card Catalog.

For more information, see What other catalogs are available?

I've checked the LC catalogs mentioned above, and it still looks like the Library doesn't have what I need. Now what?

If you believe the Library doesn't have what you are looking for, please contact a reference librarian through the Library's Ask a Librarian service.

Also try your local public or college library. Most libraries have access to a number of online databases. They can also locate and borrow items for patrons through Interlibrary Loan. Your local library is often the fastest and easiest resource for finding hard-to-find items.

Are there short URLs that I can use to bookmark the Browse, Advanced Search, and Keyword Search pages?

Yes, you can use the following short URLs to bookmark the LC Catalog search pages:

Why can't I find name and subject authority records in the LC Catalog?

While references and scope notes from the Library's name and subject authority records are integrated into LC Catalog Headings Browse Lists, full MARC 21 authority records cannot be directly searched or retrieved in the Catalog. To search authority records directly, please go to Library of Congress Authorities at []. For more information, see About Library of Congress Authorities.

What do the different numbers mean on an LC Catalog record? How do I search for these numbers?

Records in the LC Catalog contain a confusing variety of numbers, including:

Descriptions of numbers found in LC Catalog records and searching suggestions are available on the Searching Numbers and Index Descriptions help pages.

What LC Catalog support is available for Unicode? How does the Catalog handle punctuation and special characters?

The LC Catalog uses Unicode opens in a new window (UTF-8 encoding) for searching, displaying, printing, and downloading records. In 2004, all Catalog records were converted to the Unicode standard for MARC 21. In addition to Roman scripts, the Catalog contains records in the following languages/scripts: Chinese, Japanese, Korean; Cyrillic-based scripts; Greek; Hebrew, Yiddish; and Perso-Arabic script (e.g., Arabic, Persian, Pushto, Sindhi, Urdu). For more information, see Searching/Displaying Non-Roman Characters.

In general, your preferred web browser settings will not need to be changed to correctly view records that contain diacritics, special characters, or non-Roman characters. If you have problems, however, you may need to reconfigure your browser opens in a new window.

When searching the LC Catalog, most marks of punctuation in your query are converted to spaces. Some punctuation and diacritic marks are removed: apostrophes, alifs, ayns, middle dots, primes and double primes. A few special characters are retained in searches: ampersands (&), plus signs (+), at signs (@), number signs (#), and musical flat (♭) and natural (♮) signs (musical sharps are converted to spaces). Special characters are generally converted to their nearest alphabetic equivalent (for example, search an æ diagraph as ae or a þ thorn as th).

Bibliographic and holdings records can be downloaded in either MARC UTF-8 (Unicode) or MARC-8 (non-Unicode). The Library's Cataloging Distribution Service (CDS) also provides MARC 21 bibliographic and authority records in both MARC-8 and UTF-8.

Emailed bibliographic and holdings records contain a brief display (Roman script), along with a persistent link to the full LC Catalog record.

Search Results and Output

Where do I find the Library "Request in" location displayed on LC Catalog records? Can I put the item on reserve before I arrive? Does the Library allow patrons to borrow books?

Information about Library of Congress reading rooms and research centers is available on the Research and Reference Services site. This site links you to Library maps and floor plans as well as hours of operation.

While retrieving material from the Library's over 500 miles of shelving may take approximately an hour, materials can be reserved ahead of time. In addition, serious and extended researchers can request one of a limited number of individual study shelves where charged materials can be held for long term use. Note that items stored offsite may require additional time to be delivered to the Library campus.

Where do I find out more about the Library's Reader Registration program?

Public patrons of the Library's research areas are required to have a Reader Identification Card issued by the Library. 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 Catalog using their individual account numbers opens in a new window. See the Guide for Requesting Materials in the Library's Catalog opens in a new window for additional information.

If I cannot come to the Library of Congress, how do I obtain copies of items I find in the LC Catalog?

The Library of Congress does not loan material to individuals, but some items may be loaned or digitized on a case-by-case basis. You should work through your local public or institutional library's Interlibrary Loan (ILL) program to initiate a request. Usually material is available at local and regional libraries; in some cases, local libraries charge a nominal fee for processing ILL requests.

You may also purchase reproductions of some materials from the Library's Duplication Services. The Duplication Services site contains information on ordering, pricing, and Copyright clearance information.

How do I find digital versions of items in the LC Catalog?

While the LC Catalog does not link to digital versions of every item in the Library of Congress collections, thousands of Library items are available electronically, either onsite at the Library or through freely-accessible or fee-based web sites. Given the size and scope of the Library’s collections, however, the majority of Catalog records describe "physical" books, periodicals, recordings, maps, images, music scores, and other collection content.

Library collection items that have been digitized or those that are "born digital" can be accessed through URLs found in Catalog records. The LC Catalog does not generally contain links to digital versions unless the Library has digitized the content. The Library presents only those digitized works that are in the public domain. Look for the label Links in individual record displays. These links will take you either to the digital version of the item described by the record or to associated information such as publisher descriptions, tables of contents, or archival finding aids.

To help you locate ebooks and ejournals described by Catalog records, the Library also uses OpenURLs – URLs that dynamically construct web searches for full text available either onsite at the Library or through fee-based and freely-accessible web sites. When you are onsite at the Library, click the LC Find It button to locate full text content accessible from Library reading rooms. To help offsite patrons, records in the LC Catalog also 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.

You may also locate digital Library resources by directly searching other Library catalogs, such as the E-Resources Online Catalog, the Prints and Photographs Online Catalog, and the Library’s main website search.

How do I download MARC records from the LC Catalog?

Print/Save/Email/Cite Help describes how to save (download) Catalog records in either the MARC UTF-8 or MARC-8 format.

Records containing LCCNs (Library of Congress Control Numbers) can be saved in MARCXML or MODS formats from individual record displays. Titles Lists and individual record displays also support Cite, a brief text version of record metadata with minimal formatting that enables you to copy and paste citation information into text documents.

In addition, records can be exported using Z39.50/SRU, either through the LC Catalog's Z39.50 Gateway or 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.

The LC Catalog does not support emailing records in MARC formats. Emailed records are formatted as short text citations that include an LCCN Permalink back to the LC Catalog record. For example:

       Persistent Link:  []
Main title:  A Spanish renaissance songbook / edited by Charles Jacobs.
Published/Created:  University Park : Pennsylvania State University Press, c1988.
Description:  1 score (xi, 176 p.) : ill. ; 26 cm.
ISBN:  0271004355 : $22.50

CALL NUMBER:   M1623 .S74 1988 Copy 1
Request in:  Performing Arts Reading Room (Madison, LM113)

Copying records into my local database or ILS from the Catalog's MARC Tags record display fails? What are my options?

Some cataloging software enables you to import records into your database or integrated library system by copying the MARC Tags display from the LC Catalog record. If you experience problems when you copy a MARC Tags display, we recommend that you either download the MARC record directly or use the Tagged Display available in the Z39.50 Gateway. The Z39.50 Gateway is linked from LC Catalog Home and from the Additional Catalogs option of the Menu (top left of your Catalog display). This Gateway supports simple and advanced keyword searches as well as many of the left-match searches available in the LC Catalog. From your Gateway search results, click on the More on this record link, then select the Tagged Display link. Because the Gateway's tagged MARC display contains minimal HTML formatting, you should not experience copy and paste problems.

How can I reformat MARC records I've downloaded from the LC Catalog?

There are a number of third-party software products available specifically designed to manipulate and reformat MARC records, such as those from the Library's Catalog. In addition to a "card" display, most of these products also allow output in a variety of other bibliography and citation styles. A list of these products is available at: Working with MARC opens in a new window

How does relevance ranking work in my search results? What searches return relevance-ranked results?

Results of Keyword Search and searches entered in the Quick Search box are arranged in a Titles List based on their relevance to your search. The most relevant items display first, as determined by three factors:

  • Uniqueness of search terms within the database
  • Proximity of search terms to each other within the record
  • Number of different search terms present in the record

Why do some records have the legend "Library of Congress Holdings Information Not Available?"

This legend displays on LC Catalog records for:

  • Items cataloged before they are published, through the Cataloging in Publication (CIP) program. Holdings information will be added when the Library receives the actual book.
  • Items that the Library is in the process of acquiring. Holdings information will be added when the Library receives the actual material.
  • Titles for which holdings and location information could not be created during migration from legacy systems to the LC Catalog. These records are being evaluated through long-term inventory projects.

How can I find out whether the Library of Congress has a particular issue of a periodical I need?

Beginning October 1, 1999, Library staff check in new serial issues as they are received. Retrospective conversion of the older manual files will take several years. Until all titles have been converted, researchers should contact a reference librarian through the Library's Ask a Librarian service to find out whether a specific issue of a serial is held by the Library.

When I look at a record for a newspaper, the record says the Library of Congress has a complete run. But when I try to request a particular year at the Library, I'm told that the Library doesn't have it. Why is that?

Researchers commonly misinterpret the span of publication dates in records as holdings information. The Library has gradually been adding summary holdings for its newspapers. Eventually, researchers will be able to know from the LC Catalog what years of a newspaper the Library has in microfilm and bound formats.

What does the phrase [from old catalog] mean?

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. Names and subjects found on older records often contain the legend [from old catalog] to indicate possible deviations from current LC practices.

Other Library of Congress Catalogs

Where can I search the Braille and Audio catalog?

The NLS Online Catalog of the National Service for the Blind and Print Disabled is available through both a standard interface and a special accessible text-based interface. Please consult the NLS web site for additional information on NLS services.

What other catalogs are available?

In addition to the LC Catalog, the Library has expert search systems that provide access to materials in its special format collections. These separate systems (such as American Memory, Chronicling America, the Performing Arts Encyclopedia, and the Prints and Photographs Online Catalog) are gradually being replaced by the single search available from Library of Congress Home. For a more complete list, please see the Digital Collections and Programs web page.

LC Catalog records for archival collections are linked to more detailed guides are available in Finding Aids Search. Records for Library recordings can be searched in SONIC (Sound Online Inventory and Catalog).

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 Central, a web-scale discovery service, offers access to articles, ebooks, and other eresources in selected subscription and free resources available at LC.

Controlled headings for subjects, names, titles, and name/title combinations can be searched in LC Authorities. LC's Linked Data Service at also makes commonly used Library vocabularies available in RDF and other semantic-oriented formats.

Where can I search the Copyright files?

Records of the U.S. Copyright Office (including registration information and recorded documents from 1978 to the present) are available through the Copyright Catalog.