The Library of Congress Online Catalog is a database of books, serials, computer files, manuscripts, cartographic materials, music, sound recordings, and visual materials in the Library's collections.

"The Making of the Modern World: Goldsmiths'-Kress Library of Economic Literature 1450-1850" provides digital facsimile images on every page of 61,000 works of literature on economic and business published from 1450 through 1850. Fulltext searching on more than 12 million pages provides researchers unparalleled access to this vast collection of material on commerce, finance, social conditions, politics, trade and transport.

The Mohr Siebeck eBooks collection contains academic books, series and multi-volume works in the subject areas of theology, history, phiosophy, law, economics and sociology. The book selection is continuously extended by single e-book acquisitions and series purchases by MPG libraries.

The Max Planck e-Book Index provides holdings of electronic books licensed for users in the Max Planck Society.

The Max Planck Journal Index provides holdings of a great range of printed journals available within the Max Planck Society. Besides, it contains metadata of electronic journals as loaded from the EZB. The database is updated regularly from the ZDB (twice a year) and the EZB (monthly).

MPG.PuRe is the publication repository of the Max Planck Society. It contains bibliographic data and numerous fulltexts of the publications of its researchers. The repository is based on PubMan, a publication repository software developed by the Max Planck Digital Library. PuRe was introduced in the MPG in May 2009 and replaced the former institutional repository eDoc.

The library of the Max Planck Institute for the History of Science is an interdisciplinary special library focussing in its collections on the history of science. Its inventory, built up since 1994, is only available to scientists from the institute and is not part of the interlibrary loan system.

The Library of the Max-Planck-Institute for the Study of Religious and Ethnic Diversity is a specialized library with a focus on religious studies, anthropology, political science and sociology. The library does not participate in interlibrary loans but serves as a reference library to provide literature and information, mainly to the members of the Institute.

Nomos eLibrary provides access to academic books and journals in the subject areas of law, political sciences, economics, media and communication sciences, history, sociology, education and cultural studies, European Union, health sciences. The book selection has been continuously extended through the acquisition of individual eBook packages by MPG libraries. From volume 2022 onwards, access is given to the complete Nomos eBook portfolio. Max Planck researchers can publish their scientific work with Nomos as a print and in parallel as an Open Access eBook in the Nomos eLibrary. Further details are available on the MPDL website.

North American Immigrant Letters, Diaries and Oral Histories includes thousands of authors and approximately 100,000 pages of information, thus providing a unique and personal view of what it meant to immigrate to America and Canada between 1800 and 1950. Composed of contemporaneous letters and diaries, oral histories, interviews, and other personal narratives, the series provides a rich source for scholars in a wide range of disciplines. In selected cases, users will be able to hear the actual audio voices of the immigrants.

The goal of OAIster is to create a collection of previously difficult-to-access, academically-oriented digital resources that is easily searchable by anyone.

Open Syllabus is a non-profit research organization that collects and analyzes millions of syllabi to support novel teaching and learning applications. Open Syllabus helps instructors develop classes, libraries manage collections, and presses develop books. It supports students and lifelong learners in their exploration of topics and fields. It creates incentives for faculty to improve teaching materials and to use open licenses. It supports work on aligning higher education with job market needs and on making student mobility easier. It also challenges faculty and universities to work together to steward this important data resource. Open Syllabus currently has a corpus of nine million English-language syllabi from 140 countries. It uses machine learning and other techniques to extract citations, dates, fields, and other metadata from these documents. The resulting data is made freely available via the Syllabus Explorer and for academic research. The project was founded at The American Assembly, a public policy institute associated with Columbia University. It has been independent since 2019. All of the syllabi in the current collection are English language documents – including from universities where English is not the primary teaching language.

The OSF Preprints search combines records from various preprint repositories, including arXiv, bioRxiv, Cogprints, PeerJ, PsyArXiv, RePEc and SocArXiv.

Developed cooperatively with scholars and librarians worldwide, Oxford Bibliographies offers exclusive, authoritative research guides across a variety of subject areas. Combining the best features of an annotated bibliography and a high-level encyclopedia, this cutting-edge resource directs researchers to the best available scholarship across a wide variety of subjects.

The platform serves as interface to over 300 journals published by the Oxford University Press (OUP) in the humanities, social sciences, law, science, and medicine. Two-thirds of this journals are published in partnership with learned and professional societies around the world. The MPG subscription enables full text access to OUP's full journal collection. It also covers article-processing charges for Max Planck authors in hybrid and selected fully open access journals offering CC-BY licenses. Further details are available on the MPDL website.

The Oxford English Dictionary is a guide to the meaning, history, and pronunciation of over half a million words and phrases, both present and past, from across the English-speaking world. It traces the usage of words through 3.5 million quotations from a wide range of international English language sources, from classic literature and specialist periodicals to film scripts, song lyrics and social media posts.

Oxford Handbooks Online is a collection of handbooks in 17 subject areas, bringing together the world's leading scholars to write review essays that evaluate the current thinking on a field or topic, and make an original argument about the future direction of the debate. For the first time, all Handbooks are available online as well is in print across the subject areas. Monthly updates introduce articles in advance of print publication and beyond the book, online-only content ensures the most current, authoritative coverage anywhere.