Explainer · Plain-language

Coretrustseal: Definition, Meaning & Examples | CASRAI

CoreTrustSeal (CTS) is the internationally recognised certification standard for trusted data repositories. It provides a community-based, peer-reviewed mechanism through which repositories can demonstrate that they meet a set of requirements for reliability, sustainability, and data integrity. CoreTrustSeal certification is recognised by research funders and institutions as evidence that a repository is a trustworthy long-term home for research data.

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History: from Data Seal of Approval to CoreTrustSeal

The Data Seal of Approval (DSA) was established in 2008 by DANS, the Dutch national institute for data archiving. It offered a lightweight, self-assessment process in which repositories completed a questionnaire against 16 requirements and submitted to community peer review. The simplicity of the DSA made it widely adopted, particularly in Europe, and dozens of repositories received the award through the 2010s. In parallel, the International Science Council's World Data System (WDS), which certifies scientific data repositories, maintained its own membership requirements. In 2017, DSA and WDS merged their requirements to create CoreTrustSeal, with the goal of providing a single internationally recognised certification. Repositories that held DSA certification received CTS accreditation automatically in the 2017 transition (grandparenting). The CoreTrustSeal Board now governs the standard, and the requirements are periodically revised — version 2023–2025 introduced clearer evidence guidance and updated terminology.

The 16 requirements and TRUST principles

CoreTrustSeal's 16 requirements are grouped into five sections: (R0) background information about the repository; (R1–R5) organisational infrastructure including mission, licences, and continuity planning; (R6–R10) digital object management including ingest, metadata quality, data integrity, and access controls; (R11–R13) technology infrastructure; (R14) security; and (R15) ethical requirements. The TRUST principles — Transparency, Responsibility, User focus, Sustainability, and Technology — were articulated by Lin et al. in 2020 (Scientific Data, https://doi.org/10.1038/s41597-020-0486-7) as a conceptual framework for trusted data repositories. Although developed independently, they map closely onto the CoreTrustSeal requirements and are often cited together in funders' guidance on choosing a repository.

Relationship to ISO 16363 and FAIR

CoreTrustSeal sits within a recognised tiered framework of repository trustworthiness. ISO 16363 (Audit and Certification of Trustworthy Digital Repositories, based on the OAIS reference model ISO 14721) provides the most rigorous level of third-party audit, but it is expensive and time-consuming — very few repositories worldwide hold ISO 16363 certification. CoreTrustSeal provides a credible, proportionate middle tier based on community peer review rather than a paid external audit. The Data Seal of Approval formed the lowest tier. FAIR (Findable, Accessible, Interoperable, Reusable) principles and CoreTrustSeal are complementary but distinct. FAIR is concerned with the characteristics of data objects and their metadata — how discoverable and reusable individual datasets are. CoreTrustSeal is concerned with the trustworthiness of the repository as an infrastructure — whether it will continue to preserve, provide access to, and maintain the integrity of the data entrusted to it. A repository can be FAIR-enabling without being CoreTrustSeal-certified, and vice versa; ideally, a trusted repository supports both.

Key facts

At a glance

CoreTrustSeal launched 2017: merger of Data Seal of Approval (est. 2008, DANS) and World Data System (ISC/ICSU)
16 requirements across 5 domains; community peer-review process
Certified repositories include: Zenodo, UK Data Service, PANGAEA
TRUST principles (Lin et al., 2020, Scientific Data): Transparency, Responsibility, User focus, Sustainability, Technology
ISO 16363: the more rigorous (and costly) third-party audit standard for digital repositories
OAIS (ISO 14721): foundational reference model for digital preservation underlying both ISO 16363 and CoreTrustSeal

Common misconceptions

What people often get wrong

Often heard: CoreTrustSeal certification means a repository is fully FAIR-compliant.

Actually: CoreTrustSeal and FAIR address different properties. CTS assesses organisational trustworthiness and sustainability; FAIR assesses the discoverability and reusability of individual data objects. A CoreTrustSeal-certified repository is a trustworthy environment, but whether the datasets it holds are actually FAIR depends on the metadata practices of depositors and repository staff.

Often heard: Any repository claiming "trusted repository" status is CoreTrustSeal-certified.

Actually: The term "trusted repository" is not protected and is widely used informally. CoreTrustSeal certification requires a formal application, submission of evidence against 16 requirements, and community peer review. The CoreTrustSeal website maintains a registry of certified repositories that researchers and funders can consult to verify claims.

Often heard: ISO 16363 and CoreTrustSeal are the same standard.

Actually: ISO 16363 is a formal third-party audit standard based on the OAIS reference model. It is conducted by accredited external auditors and is rare and expensive. CoreTrustSeal is a community peer-review process that is less expensive and more widely adopted. Both exist within a tiered framework, with ISO 16363 providing the highest level of assurance.

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