books
WorldCat / OCLC
The world's largest union catalogue of library holdings, aggregating more than 550 million records and showing which libraries hold a given item. You search it through the web interface at search.worldcat.org. There is no longer a free API, so use the website — it remains the reference standard for locating a physical copy in a library.
degraded
Search this archive
No programmatic check — opens the archive’s own search.
Why it’s useful & how it works
No free API since v1 retired; v2 needs OCLC membership. Web UI browsable both ways. Link-only.
What’s inside
~550M+ records.
Access
Catalogue link only — open the archive to search it yourself.