Hamnet is the online catalog of the Folger Shakespeare Library's collection. It contains hundreds of thousands of records for books, manuscripts, prints, DVDs, objects, e-resources, and other material, but does not describe everything in the collection. Many manuscripts, for example, are instead described in online finding aids, and other materials are still only described in the card catalogs and other paper-based resources.
Hamnet debuted in 1997. The name was chosen through a competition open to staff and readers, and evokes both Shakespeare ("Hamnet" was the name of his son, "Hamlet" is one of his best-known plays) and the Internet (often called just "the Net" in the 1990s). At first, Hamnet only had records for open-stacks books and for newly-cataloged vault books, along with preliminary records for all vault books, art, and manuscripts acquired from 1997 onward.
Thanks to various grant-funded projects, large batches of old card catalog records were superseded by online catalog records over the years (rest assured, the card catalog still exists, it just isn't being updated anymore). Some of these records came from book-in-hand recataloging of material already cataloged on cards, but most came from retrospective conversion (known as "recon" to librarians), where someone re-types what's on the cards into the appropriate fields in an online system.
The following tips and tricks can be useful when using Hamnet. Always keep in mind, though, that standards and practices for catalog records have changed over time, that many records were created by re-keying old cards, and that people make mistakes.
Folger Tooltips: The limits of “Set Limits” in Hamnet (Collation post)
Getting a URL for a search
Folger Tooltips: Hamnet URLs, part 1 (Collation post)
Folger Tooltips: Hamnet URLs, part 2 (Collation post)
Getting raw data
Folger Tooltips: Getting raw Hamnet data (Collation post)
Specific material tips
Folger Tooltips: Hamnet access to e-books, part one (Collation post)
Manuscripts: In Hamnet, to limit search to manuscripts, search “material type” = “manuscript” under advanced search, or set date and material type limits under “set limits.”
Hamnet records are encoded in MARC (which stands for "MAchine-Readable Cataloging"), a data format developed at the Library of Congress in the late 1960s that quickly became the international standard for libraries. All MARC fields searchable from the "Advanced" tab in Hamnet are listed in Folgerpedia's List of keyword search fields in Hamnet and their associated MARC codes.