OCLC delivers quality

WorldCat represents a long-lasting collaboration among OCLC, member libraries and material providers. We maintain a system for quality bibliographic metadata creation and management. Our continuous maintenance and improvement of WorldCat records, following the guidelines in Bibliographic Formats and Standards, is central to our commitment to each other. Quality bibliographic data forms the foundation for successful discovery and sharing of library resources.

Learn more about WorldCat data standards

Sources of WorldCat bibliographic records (as of May 2023)


OCLC and member libraries 61.56%

National libraries 22.81%

Vendors/publishers 13.21%

Library of Congress 2.41%

(Items published since 2010)

Tommy Nixon [photo]

“Breadth of collections…”

“I use WorldCat on FirstSearch 10–15 times a day at least, sometimes more. I couldn't do my job without WorldCat on FirstSearch. The breadth of collections is unparalleled.”

Tommy Nixon
MLIS Subject Librarian for Classics, Dramatic Art, & English/Comparative Literature
Davis Library, University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States

OCLC staff improve WorldCat every day.

OCLC’s expert catalogers make WorldCat a valuable and unique resource for libraries worldwide, whether reviewing records uploaded in batch, adding newly cataloged records, merging duplicate records or correcting reported errors.

Our global data specialists work with libraries to review large batches of records before contributing them to WorldCat. By cleaning this data first, we increase the chances of matching new data to existing WorldCat records. The data that libraries access in WorldCat is enhanced so it’s better than the data they provided.

Due to the global nature of WorldCat, we frequently address challenges around cultural inclusion, diversity and complexity. We provide libraries with the means to contribute data to WorldCat in non-Latin script, in keeping with worldwide publishing and cataloging standards that sometimes tread on sensitive geo-political ground.

In addition, our technology specialists focus on developing unique solutions to help libraries interact with WorldCat data and manage their catalogs so local users can find and access the information they need.

Jay Weitz [photo]

“Expect more…”

“Underlying it all is the sense that our users all over the world expect more of OCLC because of who and what we are. My colleagues and I get that and keep it foremost in our minds in everything we do.”

Jay Weitz
Senior Consulting Database Specialist, Metadata Quality (Retired)
Dublin, Ohio, United States

WorldCat Quality Team

Our WorldCat Quality Team is dedicated to improving the WorldCat bibliographic catalog, knowledge base and registry. Among them, this team has more than 236 years of experience with OCLC. Our team of catalogers who focus on bibliographic and authority records—most of whom hold an MLS degree—create and enhance WorldCat records both by hand and through automated, monitored systems. From July 2021–June 2022, the WorldCat Quality Team enhanced 34,384,587 WorldCat records.

Shanna Griffith [photo]

“Improve the quality…”

“I love being a part of the WorldCat Quality Team at OCLC. We understand how important it is to our member libraries that the items in their collection are easily discovered by their patrons. As a membership cooperative, we work with our member libraries to improve the quality of existing cataloging data in WorldCat to make that possible.”

Shanna Griffith
Database Specialist II, Metadata Quality
Dublin, Ohio, United States

WorldCat Quality Team members actively participate in the Program for Cooperative Cataloging (PCC) and professional organizations, such as the American Library Association (ALA), Online Audiovisual Catalogers (OLAC) and Music OCLC Users Group (MOUG), by serving on many committees, task forces and boards. 

Enhancements by request

The WorldCat Quality Team proactively enhances records in WorldCat to reflect policy updates, such as changes to subject headings or provider-neutral coding for electronic resources. The team also reviews every WorldCat record change request submitted and determines the best action to take. Sometimes they improve only one record at a time, and sometimes they find and improve thousands of WorldCat records with similar issues. Between July 2022–April 2023, the WorldCat Quality Team received 41,901 enhancement requests.

Request a WorldCat record quality enhancement

Number of WorldCat records enhanced by the WorldCat Quality Team:

Last fiscal year:34,384,587

(July 2021–June 2022)

Current fiscal year (to date):32,397,426

(July 2022–April 2023)

Only the best version of a record

The WorldCat Quality Team maintains and monitors Duplicate Detection and Resolution (DDR) software, which processes WorldCat records to identify and merge duplicates with the help of experienced quality control catalogers. In addition to the software, the WorldCat Quality Team identifies and merges duplicates manually when appropriate. The team also responds to OCLC members' reports of duplicate records that should be merged and records that were merged inappropriately.

Learn more about cataloging defensively with DDR

Records merged annually by the WorldCat Quality Team:53,545

(July 2021–June 2022)

Duplicates removed by DDR software since August 2009:70,271,089

(as of April 2024)

Authority files to simplify cataloging

OCLC coordinates and maintains the VIAF (Virtual International Authority File) service, which aggregates the world’s major name authority files. More than 50 organizations from more than 30 countries, including many national libraries, contribute their authority files to VIAF, which then matches and links the records into a merged “super” authority record. This allows information about a single person, for example, to be discoverable no matter how that person’s name is represented in any language or character set.

Learn more about VIAF

OCLC also plays a prominent role in other worldwide authority file systems, such as ISNI (International Standard Name Identifier), the ISO-certified standard for identifying the creator of a work. OCLC hosts ISNI, and the ISNI International Agency maintains the authority files. This information feeds into VIAF and other authority databases to give a full picture of a creator across the web.

Catalogers use these authority records and others, such as the Library of Congress’s Names and Subject Authority Files, US National Library of Medicine’s Medical Subject Headings (MeSH), Koninklijke Bibliotheek’s NTA Names (Nederlandse Thesaurus van Auteursnamen), and Deutsche Nationalbibliothek’s Integrated Authority File (GND), in their regular cataloging workflows. They then add bibliographic records with standard names, subject headings and other information to WorldCat, creating new value and enriching WorldCat for libraries around the world. OCLC provides tools for displaying these authority files to catalogers and for linking the headings in bibliographic records to them. OCLC is also a node for the Library of Congress’s Name Authority File, so changes that catalogers make to this file within OCLC systems are automatically updated daily in the Library of Congress files.

Learn more about authority files

Authority records created by WorldCat Quality Team for Library of Congress Name Authority File:197

Authority records enhanced:19,274

(July 2021–June 2022)

Geoff Payne [photo]

“Attractive to the university…”

“Being able to provide researcher profiles in a way that is automatically updated by doing periodic canned searches is very attractive to academics. It's also attractive to the university, because rather than having a static research profile that goes out of date, it can be done dynamically.”

Geoff Payne
Deputy Director Strategy and Planning (retired)
La Trobe University Library
Melbourne, Victoria, Australia

A unique authoritative identifier and classification

OCLC adds its own identifying number, the “OCN,” to each record entered into WorldCat. The OCN is unique to OCLC and allows the data to be sorted and queried by OCN, in addition to other criteria, such as date, title, or author. The OCN is widely used in the library community, as well as by library vendors and publishers, as an authoritative identifier for referring to specific resources.

In addition to the proprietary OCN, OCLC also adds Dewey Decimal Classification numbers to WorldCat records. OCLC owns the Dewey Decimal Classification system, which provides an index to the subject matter of resources and gives appropriate shelf locations for items. OCLC has added Dewey numbers to more than 57 million WorldCat records.

Learn more about Dewey