Libraries of any size probably rely on the various services of a company called OCLC. No one else needs to know anything about most of them, but you may have seen a reference librarian look up something for you on WorldCat. That’s a tool you can use as easily as you use your own library’s catalog. It’s free and available from your home as well as the library.
WorldCat aspires to be a universal library catalog. It hasn’t made it yet, but it shows the holdings of about 27,000 different libraries in more than 170 different countries. Even though it does not contain the holdings of every library in the world, it easily lives up to its slogan “the world’s largest library catalog.”
You might be familiar with something similar on a smaller scale. Many people have access to more than one library. Their city’s library may have several branches. Or it might be part of a library system that includes other libraries–public, academic, and corporate. These library systems often have reciprocal borrowing agreements, so everyone who has a library card at any one library can use it to borrow things from the others. At any one library, you can look either at that library’s catalog exclusively or at the online catalogs of all the libraries in the system. Except for the reciprocal borrowing privileges, WorldCat is like that system-wide online library catalog with worldwide coverage.
Let’s say you want a particular item, look it up in your library’s online catalog (either at the library or at home), and find that they do not have it. You can go to WorldCat to see what other libraries have it. WorldCat has a place to sign in, but unless you want to be a power user, just ignore it. You will also see the familiar search box, like you would see on Google or another search engine, along with tabs to limit your search to books, CDs, DVDs, or articles, which you won’t find on Google.