interlibrary

Interlibrary refers to collaboration and resource sharing between libraries. The most common form is interlibrary loan (ILL), a service that enables libraries to lend books and other materials to patrons who are not at the owning library. Interlibrary activities also include shared catalogs, reference and research assistance, cooperative collection development, and document delivery across institutions.

Interlibrary borrowing began as a practical way to extend access to materials beyond a single library’s holdings. Over time, formal networks, regional consortia, and national programs were established to coordinate borrowing, lending, and catalog access. Many libraries participate in union catalogs, such as those facilitated by global library cooperative networks, to locate items across a broad range of institutions.

The typical ILL process starts when a patron requests an item through their home library. The library checks local holdings and, if unavailable, submits an ILL request to potential lending libraries within a network. A lending library evaluates the request, sets conditions such as loan period and restrictions, and ships the item or provides a digital copy of a article where permitted. Returns are sent back to the lending library by the patron or courier. Some items, such as rare books, reference materials, or restricted media, may not be lendable.

Materials commonly shared include books, periodical issues, microforms, audiovisual materials, and electronic articles via digital delivery. Modern ILL often involves faster electronic delivery, copyright and license considerations, and privacy protections for patrons.

Interlibrary services broaden access to resources, support research, and promote library cooperation, while requiring coordination, licensing, and logistical management among participating institutions.