Update No. 40 (June 2025) is now available on the MARC website (www.loc.gov/marc/). It is integrated into the documentation for each of the Online Full and Concise formats that are maintained on that site -- the Bibliographic format, Authority format, Holdings format, Classification format, and Community Information format. The documentation includes changes made to the MARC 21 formats resulting from proposals which were considered by the MARC 21 community since the publication of Update No. 39 (December 2024).
The changes are indicated in red. Each format also has an appendix, "Format Changes for Update No. 40 (June 2025)" that lists the changes that comprise the update. The Web version of the formats is the official version and its release is considered the start date for implementation planning for Update 40.
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