MARC — MAchine-Readable Cataloging — is the standard format that lets computers store and share a catalogue record. Each piece of information sits in a numbered field, so any library system can read a record any other library created. It is the plumbing beneath nearly every catalogue.

You’ll rarely see MARC as a user — and that’s the point. It works invisibly so that the moment one library catalogues a book, every other library can download that record instead of re-keying it. Decades old and still everywhere, MARC is quietly one of the most reused datasets in the world.

Fields, tags, and subfields

  • Numbered tags label each kind of data — 245 for title, 100 for main author, 260/264 for publication.
  • Subfields split a field into parts — in 245, $a is the title, $b the subtitle.
  • Because it’s structured, a system always knows which bit is the title and which the author — no guessing.
A title in MARC
The 245 field might read: 245 $a Things fall apart : $b a novel / $c Chinua Achebe. Cryptic at a glance — but every system on earth reads $a as the title and $c as the statement of responsibility. That shared code is what makes one library’s work usable by all.

MARC today — and tomorrow

MARC is venerable, and the field is gradually moving toward linked-data successors like BIBFRAME. But MARC still underpins most working catalogues, so understanding it remains a core cataloguing skill rather than a historical footnote.

Try this
In your library’s catalogue, look for a “staff view”, “MARC view”, or “librarian view” of any record. Spot the 245 field — you’ll see the title sitting exactly where the standard says it should.

🔗 A friendly free guide: Library of Congress — MARC Standards

MARC is one powerful way to structure description — but the wider digital world uses a simpler, more general idea for the same job. On to Metadata Basics.

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Última modificación: viernes, 5 de junio de 2026, 08:07