Library of Congress >> MARC >> Bibliographic >> Introduction


MARC 21 Bibliographic
October 2006

The five MARC 21 communication formats, MARC 21 Format for Bibliographic Data, MARC 21 Format for Authority Data, MARC 21 Format for Holdings Data, MARC 21 Format for Classification Data, and MARC 21 Format for Community Information, are widely used standards for the representation and exchange of bibliographic, authority, holdings, classification, and community information data in machine-readable form.

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).

The MARC 21 Format for Bibliographic Data: Including Guidelines for Content Designation defines the codes and conventions (tags, indicators, subfield codes, and coded values that identify the data elements in MARC bibliographic records. This document is intended for the use of personnel involved in the creation and maintenance of bibliographic records, as well as those involved in the design and maintenance of systems for communication and processing of bibliographic records. This documentation is also available online, including a concise version and a simple field list at:


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:

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

Microforms, whether original or reproductions, are not identified as a special type of record. The microform aspect is secondary to the type of material to which the original item belongs (e.g., book). The same is true for Computer Files in that the computer file aspect is secondary; however, certain categories of electronic resources are coded as Computer Files.


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.

0XX Control information, identification and classification numbers, etc.
1XX Main entries
2XX Titles and title paragraph (title, edition, imprint)
3XX Physical description, etc.
4XX Series statements
5XX Notes
6XX Subject access fields
7XX Added entries other than subject or series; linking fields
8XX Series added entries, holdings, etc.
9XX Reserved for local implementation

Within the 1XX, 4XX, 6XX, 7XX and 8XX blocks, certain parallels of content designation are usually preserved. The following meanings, with some exceptions, are given to the final two characters of the tag of fields:

X00 Personal names X40 Bibliographic titles
X10 Corporate names X50 Topical terms
X11 Meeting names X51 Geographic names
X30 Uniform titles          

Within variable data fields, the following two kinds of content designation are used:

Multiscript Bibliographic Records

A MARC bibliographic record may contain data in multiple scripts. One script may be considered the primary script of the data content of the record, even though other scripts are also used for data content. General models for multiscript data are described in Appendix D along with several examples.

Field and Subfield Repeatability

Theoretically, all fields and subfields may be repeated. The nature of the data, however, often precludes repetition. For example, a bibliographic record may contain only one 1XX main entry field; a field 100 may contain only one subfield $a (Personal name) but may contain more than one subfield $c (Titles and other words associated with a name). The repeatability or non-repeatability of each field and subfield is specified in the format.

Field Linking

Fields in the record may be specially linked using a generally-applicable field linking technique. The technique relies upon the syntax of data in subfield $8 (Field link and sequence number) to identify the linked fields. The structure and syntax for the field link and sequence number subfield are described in Appendix A.

Fill Character and Related Values

A fill character (ASCII 7C hex), represented in this document as a vertical bar (|), may be used in bibliographic records in fields 006, 007, and 008, and subfield $7 of field 533 (Reproduction note) and the linking entry fields (760-787). A fill character may not be used in the leader, or in tags, indicators, or subfield codes. The use of the fill character in records contributed to a national database may also be dependent upon the national level requirements specified for each data element. The presence of a fill character in a bibliographic record indicates that the format specifies a code to be used but the creator of the record has decided not to attempt to supply a code.

Code u (Unknown or unspecified) when it is defined indicates that the creator of the record attempted to supply a code but was unable to determine what the appropriate code should be.

Code n (Not applicable) is defined in many coded positions to indicate that the characteristic defined by the position is not applicable to a specific type of item or kind of record.

Display Constants

A display constant is a term, phrase, spacing, or punctuation convention that may be system generated in order to make a visual presentation of data in a record more meaningful to a user. In the bibliographic format certain field tags (e.g., field 770, Supplement/Special Issue Entry), indicators (e.g. field 511 Indicator 1, Display constant controller), and subfield codes (e.g., the subject subdivision subfields $x, $y, and $z in a subject added entry), may be used to generate specific terms, phrases, and/or spacing or punctuation conventions for the display of a record. The use of display constants is determined by each organization or system. Examples of display constants are provided under Input Conventions in the field descriptions.

Record Content Responsibility

The MARC 21 Format for Bibliographic Data serves as a vehicle for bibliographic data of all types from any organization. In general, the responsibility for the data content, content designation, and transcription of bibliographic information within a record may be determined by examination of the field indicated in the responsible parties section below. The data content of certain data elements, however, is restricted when the element is an agency-assigned or a controlled-list data element.

Responsible Parties

In unmodified records, the organization identified as the original cataloging source in 008/39 and/or 040 $a is responsible for the content of the record. The organization identified as the transcribing agency in field 040 $c is responsible for the content designation and transcription of the data.

In modified records, the organizations identified in 040 $a and $d (Modifying agency) are collectively responsible for the content of the record. Organizations identified as transcribing or modifying agencies in field 040 $c and $d are collectively responsible for the content designation and transcription of the data.

Agency-assigned Data Elements

An agency-assigned data element is one whose content is determined by a designated agency and is the responsibility of that agency, e.g., field 222 (Key Title) which is the responsibility of an ISSN Center. While it is usually input by the designated agency, it may be transcribed by another organization.

Controlled-list Data Elements

Certain data elements contain data from controlled lists maintained by designated agencies, e.g., the MARC Code List for Geographic Areas in field 043 (Geographic Area Code). These elements are indicated at the field or subfield level in MARC 21 and only values from the designated lists may be used. If a change or addition is desirable for a list, the maintenance agency for the list should be consulted.

Record Level Requirements

User groups may have full level and minimal level record requirements to promote consistency across cataloging agencies. These should be widely publicized for all possible interchange partners to be aware.


Main Parts

MARC 21 Format for Bibliographic Data consists of a Summary Statement of Content Designators followed by a detailed presentation of each content designator. Following the descriptions of the Leader and the Directory, the detailed presentations for each variable field are arranged in field tag order.

Appendixes to this document provide information about several control subfields (Appendix A), full level record examples (Appendix B), minimal level record examples (Appendix C), multiscript record examples (Appendix D), an alphabetical listing of ambiguous headings with suggested tagging (Appendix E), a multilingual list of initial definite and indefinite articles (Appendix F), lists of changes to the format since the last edition or update (Appendix G), a listing of several Canadian and American local fields (Appendix H) and a list of organization code sources (Appendix I).

General Information Sections

To avoid repetition, general information sections are provided for groups of fields with similar characteristics. These general information sections provide instructions for the content designators that are common to each field in the group. The description for each of the fields refers back to the general information section for that group and to any related general information section.

For example, the X00 Personal Name--General Information section is provided for personal name headings. This general information section provides instructions for the content designators that are common to each type of personal heading whether it is used in a 100 main entry field, a 600 subject access field, an 700 added entry field, or a 800 series added entry field. The description for each of the individual fields (i.e., 100, 600, 700, 800) refers back to the X00 general information section.

Components of the Detailed Descriptions

A detailed description may consist of six parts: content designator listing; character position or field definition and scope; guidelines for applying content designators, with examples; input conventions; and content designator history.

The content designator listing area presents

For the Leader and the variable control fields, the list gives the name of the character position and any defined coded value. For the variable data fields, the list gives the name of the indicator positions and any defined coded values and the name of the subfield codes and any defined coded values. For all variable fields, the repeatability/nonrepeatability code at the field level specifies whether the field may be repeated in a record. For variable data fields, the subfield repeatability code specifies whether the subfield code may be repeated within a field.

The character position or field definition and scope area describes the contents of the character position or field, the appropriateness of its use in specific kinds of bibliographic records, and gives other information, such as field repeatability in particular circumstances, the use of required lists or rules in formulating the data, etc.

The guidelines for applying content designators area describes the content and scope of each coded value, indicator, or subfield code and gives other information, such as appropriateness for use and repeatability in certain circumstances. The coded values and subfield codes in this area are presented in alphabetical/numerical order. Examples showing the use of the content designator are provided immediately following the description. The examples illustrate the application of specific MARC content designation. The data may be fuller or less full than would be used in actual cataloging practice. Most of the examples reflect the application of AACR 2 and ISBD; however, some reflect a generalized MARC application. Other examples illustrate specific points.

The input conventions area provides general guidance for the application of the content designators, and for such things as punctuation, spacing, and the use of display constants. The punctuation used within a field is generally dictated by descriptive cataloging or subject heading system/thesaurus rules. The input conventions clarify MARC punctuation practices especially with respect to final punctuation. In the discussion of punctuation practices, mark of punctuation is a period (.), a question mark (?), an exclamation mark (!), or a hyphen (-).

The content designator history area provides a record of significant content designator changes. The types of changes that are included are:

In the MARC formats, a distinction is made between obsolete and deleted content designators. An obsolete content designator is one that may have been used in MARC records and that may continue to appear in records created prior to the date it was made obsolete. Obsolete content designators are not used in new records. An obsolete content designator is recorded in the Content Designator History area. Content designation instructions are provided for retrospective conversion of records having data elements that would have been identified by the obsolete content designator. A deleted content designator is not recorded in the history area and will no longer appear anywhere in the MARC documentation. A content designator that had been reserved in MARC but has not been defined, or one that had been defined but is known with near certainty not to have been used, may be deleted from the format. A deleted content designator is available for redefinition in a format. A deleted content designator is available for redefinition in a format.

Typographical Conventions

Throughout this document, the following typographical conventions are used:

Link disclaimer


The MARC 21 Format for Bibliographic Data should be used with the following standards and related documentation. When a standard is applicable to data in specific fields of the format, the fields are given in brackets following the citation.

National and International Standards:

ISO publications may be obtained from the International Organization for Standardization (ISO) and their agents; and ANSI/NISO Z39 publications may be obtained from the National Information Standards Organization (NISO).

MARC Standards:

These publications are available from the Library of Congress, Cataloging Distribution Service, Washington, DC 20541, USA (Worldwide distribution) and Canadian Government Publishing - PWGSC, Ottawa, Ontario K1A 0S9, Canada (Canadian distribution). Where indicated these publications are available on the Internet.


This document supersedes the most recent editions of the USMARC Format for Bibliographic Data and the Canadian MARC Communication Format for Bibliographic Data. With alignment of these formats in 1997, a single edition of the format could be issued.

USMARC Documentation

MARC 21 supersedes the 1994 edition of USMARC Format for Bibliographic Data: Including Guidelines for Content Designation and updates No. 1 (March 1995), No. 2 (March 1996), and No. 3 (July 1997) to that edition. With Update No.3 the USMARC and CAN/MARC formats were identical format specifications. The 1994 edition superseded the 1988 edition of the format and its four updates published between 1988 and 1991. The 1988 edition incorporated the base text of the 1980 edition published under the title MARC Formats for Bibliographic Data (MFBD) and the 15 updates to that edition published between 1980 and 1987. The 1980 edition was a compilation of separate MARC format documents developed for different types of material and published between 1969 and 1977.

CAN/MARC Documentation

MARC 21 supersedes the 1994 edition of Canadian MARC Communication Format for Bibliographic Data and its six updates published between 1994 and 1998. Update number six contained the changes to CAN/MARC required to align with USMARC. With this update, the specifications contained in the CAN/MARC and USMARC formats were identical. The 1994 edition superseded the 1988 edition and its seven updates issued between 1988 and 1991. The 1988 edition was produced by amalgamating separately issued CAN/MARC formats for monographs and serials.


The MARC 21 Format for Bibliographic Data is prepared by the Network Development and MARC Standards Office, Library of Congress, in cooperation with Standards, Library and Archives Canada (previously National Library of Canada) and Bibliographic Standards and Systems, British Library. Please direct any questions related to the content of this document to one of the following:

Network Development and MARC Standards Office
Library of Congress
101 Independence Avenue, S.E.
Washington, DC 20540-4402, USA
Fax: +1-202-707-0115

Library and Archives Canada
395 Wellington St.
Ottawa, Ontario K1A 0N4, Canada
Fax: +1-819-934-4388

Metadata Services
The British Library
Boston Spa Wetherby
West Yorkshire LS23 7BQ, United Kingdom
Fax: +44 (0) 1937 546586

The MARC 21 Format for Bibliographic Data is organized on a field-by-field basis with each field separately paged to facilitate the updating of fields. Periodic updates of new and replacement pages for the base text and cumulated versions of the base text will be available from the Cataloging Distribution Service, Library of Congress, Washington, DC 20541-5017, USA (Worldwide distribution) and available in Canada from Publishing and Depository Services, Public Works and Government Services Canada (PWGSC), Ottawa, Ontario K1A 0S5, Canada (Canadian distribution). Their availability will be announced on the Library of Congress MARC website, the Library and Archives Canada MARC website, on listservs, and through press releases to the library press and to those who purchase the initial base volume. Updates are also available on standing order from the Library of Congress and the Canadian Government Publishing-PWGSC. This publication and all updates are supplied to all purchasers of the Library of Congress MARC Distribution Service files of bibliographic records as part of their MARC record subscription.

Library of Congress >> MARC >> Bibliographic >> Introduction
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