Transparent Ranking of Open Access Repositories – May 2025 Edition

Citation entries and patents are excluded to ensure the ranking reflects only original scholarly works.

For analytical clarity, repositories are grouped into six categories:

1. All repositories (including institutional and subject-specific)

2. Institutional repositories

3. Portals (primarily journal portals, excluding individual journals)

4. CRIS systems (Current Research Information Systems)

5. Data repositories

6. Repositories from Spain (a separate national focus)

The May 2025 edition confirms the presence of 5,528 unique OA repositories globally, reflecting both the expansion of repository infrastructures and their critical role in scholarly communication

Key Observations

Despite their importance, Google Scholar often indexes only a fraction of the items deposited in repositories. Typically, only the “main” version of a document is selected for indexing, while duplicates or secondary versions are excluded. Although Google Scholar’s method of designating the main version is not fully transparent, evidence suggests that the first version indexed is often prioritized.

This behavior has practical implications. Authors are encouraged to deposit their work first in their institutional repositories before sharing on platforms such as ResearchGate or Academia.edu, which tend to be indexed more quickly.

Metadata quality also remains a critical factor. Repositories with incomplete or inconsistent metadata may face indexing delays or penalties, reducing their visibility. Institutions are therefore advised to conduct regular metadata audits and align with Google Scholar’s indexing guidelines:
Google Scholar Inclusion Guidelines

Conclusion

The Transparent Ranking of Open Access Repositories serves as a valuable benchmarking tool for institutions and policymakers, offering insight into the reach and visibility of global research outputs. The 2025 edition not only demonstrates the continued growth of open access repositories but also underscores the challenges related to indexing accuracy, metadata quality, and repository management.

By fostering competition, transparency, and accountability, this ranking contributes to strengthening the Open Science movement and ensuring that academic knowledge remains widely accessible to scholars, practitioners, and the public at large.