Direct answer: WorldCat is a free global catalog that searches the holdings of tens of thousands of libraries at once, letting you type in a title and see exactly which nearby libraries own a physical or digital copy.
What WorldCat actually does
Run by the nonprofit OCLC, WorldCat aggregates catalog records from libraries around the world into a single searchable index. Instead of checking your city library, then the county system, then a university library one by one, you search once and see everywhere the book lives.
How to search it effectively
Search by exact title and author for the most precise match, then use the location filter to sort results by distance from your zip code. Each result links directly to that library's own catalog page, where you can place a hold with your card.
When WorldCat comes up empty
Very new releases, self-published titles, and extremely obscure books sometimes aren't indexed yet. In that case, ask your local library's reference desk directly — they can often special-order the book through interlibrary loan even if it doesn't appear in WorldCat.
WorldCat vs. a single library's own search
Your home library's website only shows its own shelves. WorldCat's advantage is breadth: it's the fastest way to discover that the county library three towns over, or a university library that allows community access, already owns the exact title you're after.
Is WorldCat free to use?
Yes, searching WorldCat is completely free and requires no account.
Can I request a book directly through WorldCat?
WorldCat itself doesn't process holds; it links you to the owning library's catalog, where you request the item using your library card.
Does WorldCat include ebooks and audiobooks?
Yes, many library digital collections are indexed alongside physical holdings, though coverage varies by library system.