Over 1,000 people participated in Bullinger’s correspondence.

10,000 letters addressed to him and 2,000 written by him are still preserved.

This correspondence is one of the most extensive of the sixteenth century. It represents a diversified and rich collection of sources enabling historical research on the past and on the former culture of Switzerland, Germany and more generally of Europe.

About 80% of the letters are written in Latin and 20% in Early New High German.

Briefverteilung Karte

Bullinger’s networking


Number of letters sent and received per location

Bullinger’s correspondence, dating from 1523 to 1575, covers a geographical area that stretches from Scotland to Belarus and from Denmark to Italy. On average, about 4.5 letters per week have been preserved.

Moreover, hardly any other correspondence of that time addresses such a wide variety of topics in such a captivating way.


About 90% of the letters are now kept in the State Archives and the Central Library of Zurich.

The remaining letters are scattered in libraries all over the world, with many of them in the Kantonsbibliothek Vadiana, St. Gallen.

Would you like to support the project?

The continuation of it depends on your sponsorship.
We are grateful for every donation.

The editorial undertaking

In the 1960s, the Swiss Reformation Studies Institute began to manually compile a card index of the approximately 12,000 letters of Bullinger’s correspondence.

The first volume of letters appeared in 1973. 20 more volumes have since followed. By the end of 2020, some 3,120 letters had been published. Each letter has been fully transcribed, explained and provided with a detailed summary.

All the volumes published so far are since October 2013 freely accessible online at This facilitates combined searches.

Since 2021, the financing of this editorial enterprise has been in jeopardy.

That is the reason why the Heinrich Bullinger Foundation was launched in December 2020.

Bullinger’s portrait – Central Library of Zurich, Department of Prints, Drawings and Photo Archive, Inv 103a

Imprint of Bullinger’s seal

Bullinger Digital

In 2019, the University of Zurich launched the project Bullinger Digital. It is supervised by Prof. Dr. Martin Volk (Institute for Computational Linguistics) and Prof. Dr. Tobias Jammerthal (Institute for Swiss Reformation History). It will be completed at the end of 2024.

The card index, which was created manually in the 1960s, is being transferred to an electronic database. The original letters kept in Zurich are digitally photographed and linked to the database.

A new OCR process will decipher the texts in the digital images. But because of the numerous writers who participated in Bullinger’s correspondence and since the state of preservation of those letters is frequently less than ideal, this will not be easy.

Furthermore, it is not enough – even though it is a valuable first step – to make original sources digitally accessible. For today’s readers, these witnesses of another time must also be explained and accurately summarised in a language still in use nowadays. Only then do they become intelligible and usable again.