Kloosterboer is a genealogical foundation dedicated to researching and documenting families with the surname Kloosterboer. Its website provides access to a family-history database covering nearly all people with this name in the Netherlands and elsewhere, as well as Klosterboer and Klosterbuer families in the United States. The site explains that these branches originated near Weener, Germany, close to the Dutch border around Bellingwolde in Groningen. The surname was used from about 1700 for farming families who leased land or farms belonging to monasteries, often on the site of an older monastery.

Visitors can explore family branches, search names, view birthdays and photographs, and consult statistics, links, and genealogical resources. The database has a public view containing information only about deceased people and a restricted view that also includes living individuals. Access to the private section is free for relatives after registration and approval. Family members are invited to submit missing details or corrections, such as birth and death information, to help improve the records.