CLOCKSS (Controlled LOCKSS) employs a unique approach to archiving (Lots of Copies Keep Stuff Safe) that was initiated by Stanford University librarians in 1999. Digital content is stored in the CLOCKSS archive with no user access unless a “trigger” event occurs. The LOCKSS technology regularly checks the validity of the stored data and preserves it for the long term.

CLOCKSS operates 12 archive nodes at leading academic institutions worldwide, preserving the authoritative versions of 30 million journal articles, over 25,000 serial and 65,000 book titles, and a growing collection of supplementary materials and metadata information. As of December 2017, 53 titles have been triggered and made available from our archive via open access. CLOCKSS participants include 310 libraries and 244 publishers.

This secure, robust, and decentralized infrastructure can withstand threats from technological, economic, environmental, and political failures. A destructive event in one location won’t jeopardize the survival of preserved digital content because the 11 other locations serve as mirror sites to back-up and repair the disrupted location’s archive.

Another CLOCKSS advantage is that publications are preserved in their original format. When an unavailable publication is triggered, the authoritative version is dynamically migrated to an accessible format via up-to-date technology.

CLOCKSS has been designated as a trustworthy repository by the Center for Research Libraries’ Certification Advisory Panel. CLOCKSS received the only perfect score for Technology.

Cite this entry: "CLOCKSS," in Open Access resources, September 29, 2018,