Today CWTS released the Leiden Ranking 2025. We in fact released two editions of the ranking, the Traditional Edition and the Open Edition. The Leiden Ranking Traditional Edition is the name we use for the Leiden Ranking based on data from the Web of Science database. The Leiden Ranking Open Edition is the name of a new edition of the Leiden Ranking launched last year based on open data from the OpenAlex database. Visitors of the Leiden Ranking website are invited to choose which edition of the ranking they would like to use (see Figure 1).

One of our strategic goals at CWTS is that “within the next few years, we want our work … to be fully based on open research information”, including open metadata of research outputs such as articles in scientific journals. To make openness of research information the norm, we are closely involved in the Barcelona Declaration on Open Research Information, launched last year and already signed by over 120 research organizations globally. The development of the Leiden Ranking Open Edition is one of the ways in which CWTS is implementing the commitment of Barcelona Declaration signatories to “make openness the default for the research information we use and produce”. At CWTS we also have the ambition to contribute to creating “a more diverse, inclusive and engaging science ecosystem”. Providing research analytics that offer a more inclusive perspective on the global academic landscape is crucial to realize this ambition.

The 2025 release of the Leiden Ranking Open Edition offers two important innovations: the inclusion of so-called non-core publications and the inclusion of a much larger number of universities. Below we discuss the significance of these innovations.

Inclusion of non-core publications

The traditional focus of the Leiden Ranking is on publications in international scientific journals, referred to as core publications in the Leiden Ranking. To offer a more inclusive view on the academic system worldwide, the 2025 release of the Leiden Ranking Open Edition also considers publications in scientific venues with a national or regional focus, referred to as non-core publications. Core and non-core publications are identified algorithmically in the OpenAlex database using the criteria documented here.

To illustrate the more inclusive perspective obtained by considering non-core publications, Figure 2 shows the profile of University of São Paulo, one of the largest Global South universities, in the Leiden Ranking Open Edition. Considering core publications only, the university has 48,926 publications in the period 2020-2023. This increases to 68,889 publications when non-core publications are considered as well, indicating that about one-third of the output of the university is excluded when the traditional perspective of core publications is taken. The profile of University of São Paulo also shows that almost one-fifth of the publications of the university are in Portuguese, reflecting the significance of non-English research outputs for the university. The case of University of São Paulo demonstrates how the 2025 release of the Leiden Ranking Open Edition offers a broader, more inclusive perspective in terms of coverage of research outputs, multilingualism, and bibliodiversity.

Figure 3 presents a world map showing per country the percentage of non-core publications of universities. Several countries stand out with high shares of non-core publications, including Indonesia, Ukraine, Russia, and several countries in Africa and Latin America. This partly reflects the impact of local open access publishing initiatives, such as SciELO and Redalyc in Latin America, as well as national open access policies in countries such as Indonesia. Perhaps surprisingly, China has only a low share of non-core publications. As discussed by others, this is an artifact resulting from metadata issues and inconsistencies in the coverage of Chinese-language journals in the OpenAlex database. There are similar challenges for other countries, for instance in Africa.

The issues observed for China and other countries show there is still a long and winding road ahead toward a fully comprehensive high-quality coverage of the global scientific publication output in databases such as OpenAlex. Nevertheless, the 2025 release of the Leiden Ranking Open Edition demonstrates the crucial role of OpenAlex in providing more inclusive research analytics.

Inclusion of larger number of universities

The Traditional Edition and the Open Edition of the Leiden Ranking 2025 include 1594 and 2831 universities, respectively. While the Traditional Edition covers all universities with at least 800 core publications in the Web of Science database in the period 2020-2023, the Open Edition covers all universities with at least 1500 core and non-core publications in the OpenAlex database in the same period. As a result of the more inclusive approach taken by the Open Edition, it covers many more universities than the Traditional Edition, in particular in countries such as India, Indonesia, and Brazil (see Figure 4).

Join the open research information transition

The innovations made in the 2025 release of the Leiden Ranking Open Edition demonstrate how open research information contributes to a more inclusive understanding of the global academic landscape, underscoring the importance of the open research information transition. If you are interested in joining the transition, we invite you to consider whether your organization can become a signatory or supporter of the Barcelona Declaration. You may also sign up to the Barcelona Declaration working groups.

CWTS supports organizations in making the open research information transition. We provide training, consultancy, and other services to help organizations make the transition. This for instance includes our training course Scientometrics Using Open Data and consultancy work such as a recent study for the National Open Research Analytics initiative in Denmark. Don’t hesitate to reach out if you would like to know more about the services we provide.

Next steps

Many universities are strengthening their commitment to open science in general and open research information in particular. Recently, four major European universities, Utrecht, Zurich, Lorraine, and Sorbonne, discontinued their participation in the Times Higher Education World University Rankings, all of them because they consider the ranking to be at odds with their commitment to openness and transparency. Hélène Boulanger, president of Université de Lorraine, recognized the Leiden Ranking Open Edition as an alternative to non-transparent rankings based on closed data:

“We need data on research to monitor public research policies. Therefore, we must prepare for the transition to an open and transparent system. In 2024, a new open and transparent ranking emerged: the open edition of the Leiden ranking. This ranking no longer relies on data from commercial databases but on those from OpenAlex and ROR, which are open and free.”

At CWTS we are fully committed to the open research information transition. Through our contribution to the Barcelona Declaration, our collaboration with UNESCO, our work on developing a so-called multiversatory, and our participation in the COMET initiative, we will keep working on improving the quality and completeness of openly available metadata of research outputs. This will enable us to further strengthen the Open Edition of the Leiden Ranking, and hopefully this will contribute to a movement away from the dominant opaque university rankings and their undue impact on the global academic system.