Although both are concerned with managing information, the occupation of archivist is quite distinct from that of librarian. The two occupations have separate courses of training, adhere to separate and distinct principles, and are represented by separate professional organisations.

Archives differ from libraries in the way that libraries hold published material (books and other printed publications), and archives hold published and unpublished material, in any format, which sometimes includes objects as well. The purpose of a library is to make material available to people, and access to publications is available through visiting the library, checking items out and reading them at home, or online. When a book is lost or has deteriorated, it is replaceable. An archive makes material available for research, but the material within an archive is rare and unique, and therefore cannot be replaced if it is lost or damaged. For this reason, archivists strive to protect and preserve their collections for current and future research, which means that there are stricter guidelines in place for accessing material. Original archival material is never taken home, for example, and some items may be unavailable for viewing in the search room if they are very fragile or unsorted/uncatalogued. Unlike in a library, digital copies (surrogates) or facsimiles may be substituted for the original.

There is much overlap between archives and libraries, as an archive may form a section of a library e.g. “Special Collections” (common in academic/university libraries), some archives contain small reference libraries, and some public archive and library services in cities are combined e.g. Liverpool Record Office, which is held within the Central Library & Archive.