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MARC 21 

MARC (MAchine-Readable Cataloging) standards are a set of digital formats for the description of items catalogued by libraries, such as books. Working with the Library of Congress, American computer scientist Henriette Avram developed MARC in the 1960s to create records that could be read by computers and shared among libraries. By 1971, MARC formats had become the US national standard for dissemination of bibliographic data. Two years later, they became the international standard. There are several versions of MARC in use around the world, the most predominant being MARC 21, created in 1999 as a result of the harmonization of U.S. and Canadian MARC formats, and UNIMARC, widely used in Europe. The MARC 21 family of standards now includes formats for authority records, holdings records, classification schedules, and community information, in addition to the format for bibliographic records.

MARC 21 was designed to redefine the original MARC record format for the 21st century and to make it more accessible to the international community. MARC 21 has formats for the following five types of data: Bibliographic Format, Authority Format, Holdings Format, Community Format, and Classification Data Format. Currently MARC 21 has been implemented successfully by The British Library, the European Institutions and the major library institutions in the United States, and Canada.

MARC 21 is a result of the combination of the United States and Canadian MARC formats (USMARC and CAN/MARC). MARC21 is based on the NISO/ANSI standard Z39.2, which allows users of different software products to communicate with each other and to exchange data.

MARC 21 allows the use of two character sets, either MARC-8 or Unicode encoded as UTF-8. MARC-8 is based on ISO 2022 and allows the use of Hebrew, Cyrillic, Arabic, Greek, and East Asian scripts. MARC 21 in UTF-8 format allows all the languages supported by Unicode.

MARC 21 is the product of the integration of USMARC, UKMARC and CANMARC (Canadian MARC). It is the most extensively used MARC format in the world and a de facto standard. It has been designed to be both a production format and an exchange format. The current maintenance agency for MARC 21 is the Library of Congress. There are five MARC 21 formats: 
  • Bibliographic
  • Authorities
  • Holdings
  • Classification
  • Community information
The future of the MARC formats is a matter of some debate among libraries. On the one hand, the storage formats are quite complex and are based on outdated technology. On the other, there is no alternative bibliographic format with an equivalent degree of granularity. The billions of MARC records in tens of thousands of individual libraries (including over 50,000,000 belonging to the OCLC consortium alone) create inertia. The Library of Congress has launched the Bibliographic Framework Initiative (BIBFRAME), which aims at providing a replacement for MARC that provides greater granularity and easier re-use of the data expressed in multiple catalogs.

Note: This article is Under Development.



  • MARC 21 Format for Bibliographic Data 
  • MARC 21 Format for Authority Data
  • MARC 21 Format for Holdings Data
  • MARC 21 Format for Classification Data
  • MARC 21 Format for Community Information
  • MARC 21 Articles and News

Library of Congress
Library of Congress [Photo by Carol M. Highsmith/Wikipedia]


A MARC record is composed of three elements: the record structure, the content designation, and the data content of the record. The record structure is an implementation of the international standard Format for Information Exchange (ISO 2709) and its American counterpart, Bibliographic Information Interchange (ANSI/NISO Z39.2). The content designation--the codes and conventions established explicitly to identify and further characterize the data elements within a record and to support the manipulation of that data--is defined by each of the MARC formats. The content of the data elements that comprise a MARC record is usually defined by standards outside the formats. Examples are the International Standard Bibliographic Description (ISBD), Anglo-American Cataloguing Rules, Library of Congress Subject Headings (LCSH), or other cataloging rules, subject thesauri, and classification schedules used by the organization that creates a record. The content of certain coded data elements is defined in the MARC formats (e.g., the Leader, field 007, field 008).

Scope of the Bibliographic Format

MARC 21 Format for Bibliographic Data is designed to be a carrier for bibliographic information about printed and manuscript textual materials, computer files, maps, music, continuing resources, visual materials, and mixed materials. Bibliographic data commonly includes titles, names, subjects, notes, publication data, and information about the physical description of an item. The bibliographic format contains data elements for the following types of material:

  • Books (BK) - used for printed, electronic, manuscript, and microform textual material that is monographic in nature.
  • Continuing resources (CR) - used for printed, electronic, manuscript, and microform textual material that is issued in parts with a recurring pattern of publication (e.g., periodicals, newspapers, yearbooks). (NOTE: Prior to 2002, Continuing resources (CR) were referred to as Serials (SE)).
  • Computer files (CF) - used for computer software, numeric data, computer-oriented multimedia, online systems or services. Other classes of electronic resources are coded for their most significant aspect. Material may be monographic or serial in nature.
  • Maps (MP) - used for all types of printed, electronic, manuscript, and microform cartographic materials, including atlases, sheet maps, and globes. Material may be monographic or serial in nature.
  • Music (MU) - used for printed, electronic, manuscript, and microform music, as well as musical sound recordings, and non-musical sound recordings. Material may be monographic or serial in nature.
  • Visual materials (VM) - used for projected media, non-projected media, two-dimensional graphics, three-dimensional artifacts or naturally occurring objects, and kits. Material may be monographic or serial in nature.
  • Mixed materials (MX) - used primarily for archival and manuscript collections of a mixture of forms of material. Material may be monographic or serial in nature. (NOTE: Prior to 1994, Mixed materials (MX) were referred to as Archival and manuscript material (AM)).

Kinds of Bibliographic Records

MARC bibliographic records are distinguished from all other types of MARC records by specific codes in Leader/06 (Type of record) which identifies the following bibliographic record types.
  • Language material
  • Nonmusical sound recording
  • Manuscript language material
  • Musical sound recording
  • Computer file
  • Projected medium
  • Cartographic material
  • Two-dimensional nonprojectable graphic
  • Manuscript cartographic material
  • Three-dimensional artifact or natural objects
  • Notated music Kit
  • Manuscript music
  • Mixed material

Components of Bibliographic Records

Description of Record Parts

A MARC bibliographic record consists of three main components: the Leader, the Directory, and the variable fields. The following information summarizes the structure of a separate MARC record. More detail is provided in MARC 21 Specifications for Record Structure, Character Sets, and Exchange Media.
  • Leader - Data elements that primarily provide information for the processing of the record. The data elements contain numbers or coded values and are identified by relative character position. The Leader is fixed in length at 24 character positions and is the first field of a MARC record.
  • Directory - A series of entries that contain the tag, length, and starting location of each variable field within a record. Each entry is 12 character positions in length. Directory entries for variable control fields appear first, sequenced by the field tag in increasing numerical order. Entries for variable data fields follow, arranged in ascending order according to the first character of the tag. The stored sequence of the variable data fields in a record does not necessarily correspond to the order of the corresponding Directory entries. Duplicate tags are distinguished only by the location of the respective fields within the record. The Directory ends with a field terminator character (ASCII 1E hex).
  • Variable fields - The data in a MARC bibliographic record is organized into variable fields, each identified by a three-character numeric tag that is stored in the Directory entry for the field. Each field ends with a field terminator character. The last variable field in a record ends with both a field terminator and a record terminator (ASCII 1D hex). There are two types of variable fields.
  • Variable control fields - The 00X fields. These fields are identified by a field tag in the Directory but they contain neither indicator positions nor subfield codes. The variable control fields are structurally different from the variable data fields. They may contain either a single data element or a series of fixed-length data elements identified by relative character position.
  • Variable data fields - The remaining variable fields defined in the format. In addition to being identified by a field tag in the Directory, variable data fields contain two indicator positions stored at the beginning of each field and a two-character subfield code preceding each data element within the field.
  • The variable data fields are grouped into blocks according to the first character of the tag, which with some exceptions identifies the function of the data within the record. The type of information in the field is identified by the remainder of the tag.

Following describe the intellectual and physical characteristics of bibliographic resources (books, sound recordings, video recordings, and so forth).




00X - Control Fields-General Information

001 Control Number
003 Control Number Identifier
005 Date and Time of Latest Transaction
006 Fixed-Length Data Elements -- Additional Material Characteristics
007 Physical Description Fixed Field
008 Fixed Length Data Elements


01X-09X - Control Information, Number and Codes-General Information

010 Library of Congress Control Number
013 Patent Control Information
015 National Bibliography Number
016 National Bibliographic Agency Control Number
017 Copyright or Legal Deposit Number
018 Copyright Article-Fee Code
020 International Standard Book Number
022 International Standard Serial Number
024 Other Standard Identifier
025 Overseas Acquisition Number
027 Standard Technical Report Number
028 Publisher or Distributor Number
030 CODEN Designation
031 Musical Incipits Information
032 Postal Registration Number
033 Date/Time and Place of an Event
034 Coded Cartographic Mathematical Data
035 System Control Number
036 Original Study Number for Computer Data files
037 Source of Acquisition
038 Record Content Licensor
040 Cataloging Source
041 Language Code
042 Authentication Code
043 Geographic Area Code
044 Country of Publishing/Producing Entity Code
045 Time Period of Content
046 Special Coded Dates
047 Form of Musical Composition Code
048 Number of Musical Instruments or Voices Code
050 Library of Congress Call Number
051 Library of Congress Copy, Issue, Offprint Statement
052 Geographic Classification
055 Classification Numbers Assigned in Canada
060 National Library of Medicine Call Number
061 National Library of Medicine Copy Statement
066 Character Sets Present
070 National Agricultural Library Call Number
071 National Agricultural Library Copy Statement
072 Subject Category Code
074 GPO Item Number
080 Universal Decimal Classification Number
082 Dewey Decimal Classification Number
083 Additional Dewey Decimal Classification Number
084 Other Classification Number
085 Synthesized Classification Number Components
086 Government Document Classification Number
088 Report Number
09X Local Call Numbers

Heading Fields - General Information Sections

X00 Personal Names-General Information
X10 Corporate Names-General Information
X11 Meeting Names-General Information
X30 Uniform Titles-General Information

1XX - Main Entries-General Information

100 Main Entry-Personal Name
110 Main Entry-Corporate Name
111 Main Entry-Meeting Name
130 Main Entry-Uniform Title

20X-24X - Title and Title-Related Fields -- General Information

210 Abbreviated Title
222 Key Title
240 Uniform Title
242 Translation of Title by Cataloging Agency
243 Collective Uniform Title
245 Title Statement
246 Varying Form of Title
247 Former Title

25X-28X - Edition, Imprint, Etc. Fields - General Information

250 Edition Statement
254 Musical Presentation Statement
255 Cartographic Mathematical Data
256 Computer File Characteristics
257 Country of Producing Entity
258 Philatelic Issue Data
260 Publication, Distribution, etc. (Imprint)
263 Projected Publication Date
264 Production, Publication, Distribution, Manufacture, and Copyright Notice
270 Address

3XX - Physical Description, Etc. Fields - General Information

300 Physical Description
306 Playing Time
307 Hours, Etc.
310 Current Publication Frequency
321 Former Publication Frequency
336 Content Type
337 Media Type
338 Carrier Type
340 Physical Medium
342 Geospatial Reference Data
343 Planar Coordinate Data
344 Sound Characteristics
345 Projection Characteristics of Moving Image
346 Video Characteristics
347 Digital File Characteristics
348 Format of Notated Music
351 Organization and Arrangement of Materials
352 Digital Graphic Representation
355 Security Classification Control
357 Originator Dissemination Control
362 Dates of Publication and/or Sequential Designation
363 Normalized Date and Sequential Designation
365 Trade Price
366 Trade Availability Information
370 Associated Place
377 Associated Language
380 Form of Work
381 Other Distinguishing Characteristics of Work or Expression
382 Medium of Performance
383 Numeric Designation of Musical Work
384 Key
385 Audience Characteristics
386 Creator/Contributor Characteristics
388 Time Period of Creation

4XX - Series Statements - General Information

490 Series Statement

5XX - Notes-General Information

500 General Note
501 With Note
502 Dissertation Note
504 Bibliography, Etc. Note
505 Formatted Contents Note
506 Restrictions on Access Note
507 Scale Note for Graphic Material
508 Creation/Production Credits Note
510 Citation/References Note
511 Participant or Performer Note
513 Type of Report and Period Covered Note
514 Data Quality Note
515 Numbering Peculiarities Note
516 Type of Computer File or Data Note
518 Date/Time and Place of an Event Note
520 Summary, Etc.
521 Target Audience Note
522 Geographic Coverage Note
524 Preferred Citation of Described Materials Note
525 Supplement Note
526 Study Program Information Note
530 Additional Physical Form Available Note
533 Reproduction Note
534 Original Version Note
535 Location of Originals/Duplicates Note
536 Funding Information Note
538 System Details Note
540 Terms Governing Use and Reproduction Note
541 Immediate Source of Acquisition Note
542 Information Relating to Copyright Status
544 Location of Other Archival Materials Note
545 Biographical or Historical Data
546 Language Note
547 Former Title Complexity Note
550 Issuing Body Note
552 Entity and Attribute Information Note
555 Cumulative Index/Finding Aids Note
556 Information about Documentation Note
561 Ownership and Custodial History
562 Copy and Version Identification Note
563 Binding Information
565 Case File Characteristics Note
567 Methodology Note
580 Linking Entry Complexity Note
581 Publications About Described Materials Note
583 Action Note
584 Accumulation and Frequency of Use Note
585 Exhibitions Note
586 Awards Note
588 Source of Description Note
59X Local Notes

6XX - Subject Access Fields - General Information

600 Subject Added Entry-Personal Name
610 Subject Added Entry-Corporate Name
611 Subject Added Entry-Meeting Name
630 Subject Added Entry-Uniform Title
647 Subject Added Entry-Named Event
648 Subject Added Entry-Chronological Term
650 Subject Added Entry-Topical Term
651 Subject Added Entry-Geographic Name
653 Index Term-Uncontrolled
654 Subject Added Entry-Faceted Topical Terms
655 Index Term-Genre/Form
656 Index Term-Occupation
657 Index Term-Function
658 Index Term-Curriculum Objective
662 Subject Added Entry-Hierarchical Place Name
69X Local Subject Access Fields

70X-75X - Added Entries - General Information

700 Added Entry-Personal Name
710 Added Entry-Corporate Name
711 Added Entry-Meeting Name
720 Added Entry-Uncontrolled Name
730 Added Entry-Uniform Title
740 Added Entry-Uncontrolled Related/Analytical Title
751 Added Entry-Geographic Name
752 Added Entry-Hierarchical Place Name
753 System Details Access to Computer Files
754 Added Entry-Taxonomic Identification

76X-78X - Linking Entries-General Information

760 Main Series Entry
762 Subseries Entry
765 Original Language Entry
767 Translation Entry
770 Supplement/Special Issue Entry
772 Supplement Parent Entry
773 Host Item Entry
774 Constituent Unit Entry
775 Other Edition Entry
776 Additional Physical Form Entry
777 Issued With Entry
780 Preceding Entry
785 Succeeding Entry
786 Data Source Entry
787 Other Relationship Entry

80X-83X       Series Added Entries-General Information

800 Series Added Entry-Personal Name
810 Series Added Entry-Corporate Name
811 Series Added Entry-Meeting Name
830 Series Added Entry-Uniform Title

841-88X - Holdings, Alternate Graphics, Etc.-General Information

850 Holding Institution Full | Concise

852 Location

856 Electronic Location and Access

880 Alternate Graphic Representation

882 Replacement Record Information

883 Machine-generated Metadata Provenance

884 Description Conversion Information

885 Matching Information

886 Foreign MARC Information Field

887 Non-MARC Information Field

Library of Congress
Library of Congress [Photo credit: Carol M. Highsmith/Wikipedia]


Provide information about individual names, subjects, and uniform titles. An authority record establishes an authorized form of each heading, with references as appropriate from other forms of the heading.

This section chiefly draws information from NACO Participants' Manual⁴ and Library of Congress MARC 21 Format for Authority Data⁵.

670 - Source Data Found (R) - MARC 21 Authority

Library of Congress
Library of Congress [Photo by Library of Congress/Wikipedia]


Provide copy-specific information on a library resource (call number, shelf location, volumes held, and so forth).

Library of Congress
Library of Congress [Photo by Mr. Gray/Wikipedia]


MARC records containing classification data. For example, the Library of Congress Classification has been encoded using the MARC 21 Classification format.

Library of Congress
Library of Congress [Photo by Ricardo Gomez Angel/Unsplash]


MARC records describing a service-providing agency, such as a local homeless shelter or tax assistance provider.



---------- Forwarded message ---------
Date: Tue, Jul 28, 2020 at 5:52 PM
Subject: [SACOLIST] Announcement: New coding in proposals
To: <>

Hello SACO members,

This message details new coding that catalogers in SACO institutions are to use when making proposals for subject headings, genre/form terms, and medium of performance terms. These new instructions support LC’s linked data efforts, and are effective immediately.

According to longstanding policy, field 670 subfield $a contains the LC bibliographic record control number (i.e., the LCCN) if applicable, the main entry, the title, and the publication date of the work. 

The LCCN will now be coded in subfield $w, which will be the final element of the field. The LCCN is preceded by LC’s MARC organization code, DLC, enclosed in parentheses. Example:

            Citation formatted according to former policy:
670 ## $a Work cat: 2015300502: Finding Julia, 2014: $b p. 13 (Bollinger family) p. 11 (Bollinger County, Missouri was named after George Frederick Bollinger, b. 1770. His German ancestors migrated from Zurich, Switzerland to Philadelphia in 1738)

            Citation formatted according to new policy:
670 ## $a Work cat: Finding Julia, 2014: $b p. 13 (Bollinger family) p. 11 (Bollinger County, Missouri was named after George Frederick Bollinger, b. 1770. His German ancestors migrated from Zurich, Switzerland to Philadelphia in 1738) $w (DLC)2015300502

Catalogers in SACO institutions must provide the LCCN in 670 subfield $w when the proposal is made for a CIP cataloged in LC’s CIP Partnership Program.

“Work cat” citations in other SACO proposals may contain a single subfield $w that reflects either the local control number of the SACO institution or a bibliographic utility control number (e.g., the OCLC number). If provided, the number should be preceded by the MARC organizational code to which the control number applies (e.g., $w (OCoLC)236328585). Subfield $w is not required for SACO proposals, other than for those proposals made to support CIP cataloging.

Catalogers making a proposal to revise an existing record should code the new “Work cat.” citation in the new way, but should not revise the existing citations. Do not revise citations in existing authority records to move to subfield $w an LCCN that appears in subfield $a, nor to add a control number to a citation that does not currently include a control number.

The new coding is required only in “Work cat.” citations, not in citations for reference sources. The new policy affects only proposals for subject headings, genre/form terms, and medium of performance terms. It does not impact name authority records.

Beginning September 1, PTCP will return miscoded proposals to catalogers for correction before the proposal will be scheduled for a list.

The new policy on 670 subfield $w is documented in Subject Headings Manual (SHM) H 200 sec. 9.a., and the templates in the Proposal System have been updated to remind catalogers to use the new subfield. 




1. Library of Congress. MARC Standards (accessed October 10, 2017)

2. Wikipedia. MARC standards. (accessed October 10, 2017)

3. IFLA. Best Practice for National Bibliographic Agencies in a Digital Age  (accessed October 10, 2017)

4. Library of Congress. NACO Participants Manual.'Manual-20200708.pdf (August 5, 2020).

5. Library of Congress. MARC 21 Format for Authority Data. (August 5, 2020).

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