By Megan Carter, Library Resources Editor · Updated August 9, 2026

What is interlibrary loan?

Interlibrary loan (ILL) is a service that lets your library borrow a book — or get a copy of an article — from another library when it doesn't own the item itself. You don't contact the other library yourself: you place a request with your own library, and library staff locate a copy elsewhere, arrange the loan, and have it shipped to your branch for you to pick up. When you're done, you return it to your library and it's mailed back. In effect, ILL turns thousands of separate library collections into one enormous shared catalog you can borrow from with your existing library card.

The service works because most libraries share their holdings through a common network. In the United States, the backbone is OCLC's WorldCat — a global catalog that combines millions of records and billions of holdings from more than 10,000 libraries — and the WorldShare Interlibrary Loan system libraries use to send requests to one another. Many public libraries also belong to regional or statewide consortia that make borrowing between nearby libraries even faster and cheaper. If one library can't fill your request, the system automatically routes it to the next library that owns a copy.

How to request an interlibrary loan

There's usually more than one way to start a request. Many library catalogs have a “Request interlibrary loan” or ILL form built in; you can also search WorldCat.org to confirm the item exists and send a request from there; or you can simply ask a librarian in person, by phone, or by email. Whichever route you choose, the more identifying details you provide, the faster staff can find a copy.

One reason it helps to go through a librarian is that they can see each potential lending library's holdings, policies, and any fees before sending your request — and steer it toward a library that will fill it quickly and for free. If your library belongs to a regional or statewide consortium, staff will usually check that shared network first, since those loans are typically the fastest and least likely to carry a charge.

How much does interlibrary loan cost?

For most public library patrons, ILL is free — many libraries absorb the cost as a standard service. That said, policies vary widely, so treat any dollar figure as a range and confirm with your library before you request. Some libraries charge a small per-item processing fee, and a few pass along charges when the lending library itself charges to loan an item — which is more common for hard-to-find, rare, or international requests. As one example, the Library of Congress lends free to U.S. libraries but charges international libraries a set fee per book or article scan. The key rule: ask your library what (if anything) an ILL will cost, and ask to be notified before any fee is applied.

How long does interlibrary loan take?

Plan ahead: interlibrary loan is not instant. A typical book request often arrives in about one to two weeks, but delivery can range anywhere from a few days to several weeks depending on how far the lending library is, how rare the item is, and shipping times. Requests filled through a nearby regional consortium tend to be on the faster end, while rare or international items take longer. Article scans and document delivery are usually much quicker — sometimes just a day or two — because they're delivered electronically by email rather than shipped.

What can (and can't) be borrowed through ILL

Regular circulating books are the bread and butter of interlibrary loan, and you can often get older, out-of-print, scholarly, or niche titles your library would never stock. But every lending library sets its own rules, so some categories are commonly restricted or refused:

Often restricted or not loaned: brand-new bestsellers (the owning library needs them for its own patrons), reference materials, rare books and special collections, genealogy and archival items, audiovisual media in some systems, and textbooks (hard to find available and you usually can't keep them for a full semester). Whole bound journal volumes generally aren't loaned either — but you can request an article scan instead.

That's where document delivery comes in: instead of shipping a physical journal, the lending library scans the specific article or chapter you need and emails you a copy. It's fast, and copies are yours to keep (subject to copyright limits), so it's the best route for research and periodicals.

Loan periods, renewals, and returns

Because the item belongs to another library, the lending library sets the due date — and it's frequently shorter than your library's normal loan (loan periods commonly fall somewhere in the range of a few weeks). You'll pick the item up at your home library, and you return it there too; staff handle mailing it back.

Renewals are never guaranteed. Whether you can extend an ILL item is entirely up to the lending library, and some items can't be renewed at all. If you think you'll need more time, ask your library to request a renewal before the due date. Also watch for use restrictions the lender may attach — occasionally an item is marked “library-use only” or “no photocopying.” When in doubt, your librarian is the best guide to your specific request.

Frequently Asked Questions