ChatGPT SearchSep 16, 2026
MARC 21 is a widely used machine-readable bibliographic format and underpins many library catalogs.
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Data as of Oct 14, 2026Based on 1,789 AI responses
Reviewed by Dimitry Apollonsky
Library of Congress provides online documentation for the MARC 21 Format for Bibliographic Data, offering both full and concise field descriptions, examples, and update history, including updates through May 2026. The site groups the data elements into sections (Leader, Directory, 00X–09X control fields, 1XX main entry fields, 2X–9X title and related fields, 3XX–4XX physical description and series, 5XX notes, 6XX subject access, 70X–75X added entries, 76X–78X linking fields, 80X–83X series added entries, and 841–88X holdings) and provides appendices with examples and data element lists. It serves as a reference for librarians and developers implementing MARC 21 bibliographic records, including guidance on local data elements, data provenance, and related organization code sources.
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of 1,789 answers across MARC 21’s markets · since Jul 5
The market map
Library Management SystemsMentioned in
Question: I'm a school librarian. What's the best way to create a digital catalog of our library's resources?
ChatGPT SearchSep 16, 2026
MARC 21 is a widely used machine-readable bibliographic format and underpins many library catalogs.
Share of answers in Library Management Systems each week · 422 answers since Jul 5
Each engine’s share of its own answers across MARC 21’s markets · since Jul 5
Where MARC 21 ranks in AI
Excerpts where MARC 21 appeared in the AI's answer
MARC 21 is a widely used machine-readable bibliographic format and underpins many library catalogs.
