How we preserve the hard work and knowledge of scholars

As libraries and publishers around the world migrate from print to online-only publications, they need assurance that their investments are protected and preserved for generations to come. CLOCKSS exists to provide these assurances.

As a digital archive, CLOCKSS preserves a online scholarly content. This unique service enables authors, libraries, and publishers to be confident that the content they produce and steward will withstand potential technological, economic, environmental, and political disruptions. Your contributions to the scholarly record will always be available to those who want to access it, after a trigger event has occurred.

Find out more about CLOCKSS and why we are trusted by the world’s leading research libraries and academic publishers.

E-book library concept with laptop computer and stack of books on wooden table

World Leading Digital Archive Technology

Built with proven LOCKSS open-source technology, CLOCKSS preserves scholarly publications in original formats. The polling-and-repair mechanism ensures the long-term validity of the data. Content is migrated to the latest formats when triggered in order to remain usable.

The LOCKSS technology safeguards against the long-term, well-documented causes of digital loss: human error, computer attacks, economic and organizational failure.

Mirror repository sites at 12 major academic institutions around the world guarantee long-term preservation and access. Our approach is resilient to threats from potential technological, economic, environmental, and political challenges.

CLOCKSS assigns Creative Commons Open Access licenses to all triggered publications to ensure they are always open and available to everyone.

Click here to find out more about the benefits and services we can offer to both the library and publishing communities.

Technical overview

The following is a step-by-step overview of how content flows into CLOCKSS and is preserved.

Step One
The publisher signs an agreement that gives CLOCKSS preservation rights in perpetuity, and provides content to the CLOCKSS system.


To allow CLOCKSS access to the publisher's source files, the publisher needs to place them on a designated FTP site.


Step Two
Special CLOCKSS boxes located at Rice, Indiana, and Stanford Universities ingest the content the publisher makes available.


Step Three
The content in each CLOCKSS box must go through a verification process to confirm that each holds a version of the content that is identical to each of the others. This establishes the authoritative version of the content.


Step Four
After the quality of the content on the ingest machines is validated, it is collected from them by the preservation CLOCKSS boxes. The majority of the CLOCKSS boxes are preservation machines, performing the main storage and audit functions.


Step Five
The content is then preserved through a system of audit and repair. The CLOCKSS boxes continually communicate over the Internet to audit the content they are preserving. If the content in one CLOCKSS box is damaged or incomplete, that CLOCKSS box will receive repairs of the content based on other CLOCKSS boxes' holdings and/or by referring to the publisher's original presentation files. This cooperation between the CLOCKSS boxes avoids the need to back each up individually. It also provides unambiguous reassurance that the system is performing its function and that the correct content is always available.


Step Six
When a trigger event occurs and the CLOCKSS Board decides to release the content from the CLOCKSS Archive, two things happen:

a. Content is migrated to the newest format so that it remains usable.
b. Content is copied from the CLOCKSS boxes to a publicly available web server at a CLOCKSS host organization (currently the University of Edinburgh Library and Stanford University Library).


Step Seven
The released content is now freely available from Stanford University and EDINA at the University of Edinburgh. It is also directly available via Open URLs through Crossref, or either of:

  1. local library link-resolvers
  2. from this list

Figure (a)


Figure (b)

E-book library concept with laptop computer and stack of books on wooden table

Working with CLOCKSS

Sustainable organization governed by its Board
CLOCKSS is a collaboration between world leading research libraries and academic publishers. CLOCKSS is a financially secure, independent non-profit 501(c)(3) organization, governed by its Board of libraries and publishers.

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