About CLOCKSS
CLOCKSS is an international long-term digital preservation service dedicated to preserving academic content. Established as a not-for-profit in 2008, CLOCKSS is community owned and governed jointly by academic libraries and publishers. We are part of the community of preservation services built around LOCKSS open-source software developed by Stanford University.
CLOCKSS preserves content curated or published in more than 80 countries around the world. We are independently audited against the ISO 16363 standard for trustworthy digital repositories and received the highest score ever awarded through a TRAC audit by the Center for Research Libraries (CRL).
CLOCKSS provides a dark archive of digital scholarly content. Content remains securely preserved and private unless a "trigger event" - such as the failure of a publisher or hosting platform - puts it at risk of becoming unavailable.
The fundamental principle behind CLOCKSS is distributed preservation. Rather than relying on a single institution, data center, or jurisdiction, CLOCKSS maintains multiple, independently managed copies of preserved content across geographically dispersed nodes. These copies continuously check one another, enabling the system to detect corruption and repair damaged copies from healthy ones.
This architecture provides an important additional layer of resilience. A preservation copy located only within one institution or country remains exposed to risks that are geographically or institutionally concentrated: infrastructure failure, natural disasters, cyber incidents, institutional failure, or changes in the legal or political environment. CLOCKSS deliberately distributes those risks across institutions and jurisdictions.
About the CLOCKSS Nodes
All content preserved in the CLOCKSS archive is stored securely across a network of geographically distributed nodes. These nodes are hosted by established research and library organisations in different regions of the world.
Current and planned node host organizations are:
- Australian National University
- Humboldt University-Berlin
- Indiana University
- National Institute of Informatics
- OCLC Online Computer Library Center
- Rice University
- Stanford University
- Università Cattolica del Sacro Cuore
- University of Alberta
- University of Edinburgh – EDINA
- University of Virginia
- From 2027, the Committee of Higher Education Libraries of South Africa (CHELSA)
The geographical distribution is deliberate. CLOCKSS does not simply make multiple copies; it separates those copies across independent institutions and jurisdictions. This means that a problem affecting one organization’s infrastructure, environment, region, or country does not automatically put all preservation copies at risk.
This is particularly important for scholarship. Preserving content internationally means that the archive itself does not depend on the continued availability of infrastructure or institutions within any single country.
Why independent nodes matter
The nodes are not simply backup servers. They form part of the CLOCKSS coordinated preservation network in which independently managed copies provide resilience to one another.
A single-country preservation arrangement can provide valuable protection against accidental deletion or hardware failure, but it cannot provide the same protection against geographically concentrated risks. For example, a major infrastructure failure, natural disaster, cyber incident, institutional failure, geopolitical change, or other event affecting a particular region could potentially affect both the original content and any preservation copies.
CLOCKSS reduces this concentration of risk by placing preservation copies in different institutions and countries. The result is a distributed chain of trust and resilience rather than a single point of dependence.
The node host organizations also provide an important element of institutional independence. Each host must be part of an organisation with an established long-term commitment to the preservation of scholarly content and must meet the requirements set out in the CLOCKSS Bylaws.
What do the node host institutions do?
The CLOCKSS nodes are part of both the technical and social infrastructure of the archive. This combination is deliberate: CLOCKSS distributes not only copies of content, but also responsibility for its stewardship. This matters because digital preservation is not simply a technical problem. A preservation system must remain trusted, supported and sustainable over decades and centuries.
Social Governance
Part of the reason that CLOCKSS holds the highest TRAC audit score ever awarded is because of our social governance.
CLOCKSS is a community owned and controlled archive, and our node host organizations play an important role in regional advocacy for digital preservation generally and preservation with CLOCKSS. They champion and encourage more libraries and publishers to take digital preservation seriously.
Becoming a node host organization is a very long-term commitment, so having a community of support from other organizations in your region can help sustain support over the long-term and ensure that at times of change - for example when a Library Director retires - support continues.
Node host organisations are also represented on the CLOCKSS Board of Directors, giving them a formal role in the governance of the archive.
Financial contribution
Hosting a CLOCKSS node involves a significant financial commitment. Each node host contributes at the highest CLOCKSS membership fee tier, currently $18,350 per year.
This financial commitment is another indication that node hosting is a substantive institutional responsibility rather than a technical hosting arrangement. In some regions, a consortium or community of institutions provide additional resilience and support to help sustain the commitment over the long term.
Technical responsibilities
CLOCKSS has a very robust approach to security. You can read more about it here: Understanding CLOCKSS Security.
Each node host stores and manages CLOCKSS servers in a secure data centre, with physical security, access controls, monitoring and operational safeguards comparable to those applied to its own critical infrastructure.
The distributed architecture provides an additional layer of security and resilience beyond the security measures applied at any individual node. Copies are independently maintained and continuously checked, so that the network can detect discrepancies between copies and recover from corruption or other failures.
In this sense, the security of CLOCKSS does not depend on every individual node being perfect. Our strength comes from combining secure individual nodes with geographic distribution, institutional independence, continuous integrity checking, and multiple preservation copies.
That is the key distinction between CLOCKSS and a preservation strategy based solely on keeping content within one institution or one country: CLOCKSS is designed so that the failure or compromise of any one part of the system does not become the failure of the archive as a whole.
Conclusion
A distributed network is intrinsically more resilient than a single-country or single-institution archive.
- Independence - the archive is not dependent on any single institution, country, government, legal regime, or infrastructure environment.
- Geographic distribution - copies are widely separated, thereby reducing exposure to natural disasters, regional outages, political events and other geographically concentrated risks.
- Self-healing - nodes continuously compare copies and identify and repair any corrupted content.
- Secure, dark infrastructure - the nodes are not mirrors of one another and play an active role in ensuring the authenticity and integrity of the content with the CLOCKSS archive. Access is very tightly controlled, with the archive remaining dark (i.e. inaccessible to human or machine users) unless a pre-defined trigger event occurs.