The Erasmus Collection of Rotterdam City Library is one of the world's largest, if not the largest. Apart from its own collection the Library also possesses a unique card index containing bibliographical descriptions of about 6,000 editions of Erasmus’s works. They encompass Latin texts as well as translations. Each edition is accompanied by its present location thanks to data collected among hundreds of libraries throughout the world. Bibliographical references are added in many cases as well.

The Vault Rotterdam City Library's vault hosts the world's largest collection of Erasmiana printed before 1800.

The initiator of this file is Egbertus van Gulik, MA (1910–1998). Educated as a historian, he was librarian of Rotterdam City Library from 1961 to 1973. Between 1965 and 1989 he was a member of the Conseil international pour l’édition des oeuvres complètes d’Erasme. His major work on Erasmus’s private book collection will be published posthumously by University of Toronto Press.

Starting-point for Van Gulik’s index was the “Bibliotheca Erasmiana”, a provisional repertoire of Erasmus’s works, published by Ferdinand vander Haeghen in 1893. The information on library locations and the bibliographical references basically reflect the situation as it was by 1970. Although entries have since been regularly added and updated, this was not done in a systematic or comprehensive way.

The international world of scholarship attaches great importance to this card index named after Van Gulik. It is the starting-point for any serious study of Erasmus’s works. For this reason it was decided to digitize the index and to publish it here under the name Erasmus Online, thus making it accessible worldwide. Erasmus Online offers a modern search functionality enabling complicated search actions such as: all editions of the “Praise of Folly” published between 1520 and 1530 but not in Antwerp. Over 2,000 editions include an illustration of the title page as well. Seventeen editions (including two Collected Works editions) have been digitized fully. All this makes Erasmus Online a useful tool not only for philologists and historians, for book historians, philosophers and theologians, but for booksellers and auctioneers as well.

This database is a work in progress. Since both Van Gulik’s index and Vander Haeghen’s repertoire are inexhaustive according to modern scholarly standards, their contents are continuously enlarged and updated. In the course of time a comprehensive bibliographical description of each title entry will be provided. Texts by Erasmus himself have also been made available here — Latin originals (already) as well as (in due course) translations that played an important role in the past. Erasmus Online opens up these texts in a simple way for all to use free of charge.

This digitizing project was made possible thanks to generous financial support from the foundations Erasmusstichting in Rotterdam and Stichting Bevordering van Volkskracht in Rotterdam. Realization has occurred in conjunction between the Erasmus Center for Early Modern Studies, Brill Publishers (olim IDC) of Leiden and Trilobiet Internet Services in Rotterdam. IDC initiated this project and developed the database. The application was developed by Trilobiet.

Prof. dr. Hans Trapman, secretaris van de Conseil international pour l’édition des oeuvres complètes d’Erasme

Erasmus Online was initiated by IDC Publishers and has been developed by IDC for the Erasmus Center for Early Modern Studies.

IDC Publishers, founded in 1957, specializes in providing access to rare primary sources for the scholarly community. Among its publications are sources on the Lutheran Reformation, Philosophy and the Liberal Arts in the Early Modern Period, Early Printed Bibles, and a vast collection of Sixteenth-Century Pamphlets. The latter IDC collection includes many rare writings by Erasmus.

IDC Publishers is based in Leiden, the Netherlands.

The website and the search application have been developed by Trilobiet Internet Services.

Trilobiet builds applications opening up data collections via the Internet. Based on its expertise Trilobiet has developed internet and intranet applications as well as websites for a variety of archives and educational institutions, museums and authorities. Trilobiet Internet Services is based in Rotterdam.