Over more than five centuries the Vatican Library has accumulated one of the world's most significant collections of manuscripts spanning classical antiquity, the medieval Christian and Islamic worlds, and the Renaissance, including biblical manuscripts, patristic texts, and scientific treatises, alongside a body of material connected to the history of astrology, alchemy and esoteric thought that the Church itself often regarded with official suspicion even as it preserved manuscripts documenting these traditions for scholarly and administrative purposes.
The Vatican Secret Archive, administratively distinct from the Library proper though historically linked to it, has periodically opened long restricted document series to scholars, including material connected to the Roman Inquisition, a process of gradual disclosure that has drawn sustained scholarly interest. Access to the Library has historically been restricted to qualified scholars presenting a specific research need rather than open to the general public, a policy that has drawn periodic criticism from historians frustrated by slow or selective access to sensitive holdings, though the Library has expanded access considerably in recent decades. Since the early twenty first century the Vatican Library has pursued a large scale digitization program in partnership with international academic institutions, making high resolution images of thousands of its most significant manuscripts freely available online, a substantial shift toward public access for an institution historically defined by its restrictions.