• 19.10.1909 : born in Roux. Secondary education (humanities) in Binche.
• 16.11.1939 : doctorate in philosophy and literature (philosophy) in Brussels (central jury).
• 15.12.1939 : trainee at the Royal Library of Belgium.
• 22.01.1941 : first class librarian.
• 1946 : co-founder and administrator of the publication Scriptorium with Camille Gaspar and Frédéric Lyna.
• 01.12.1952 : deputy curator of the Manuscripts Section.
• 22.04.1958 : curator of the Manuscripts Section.
• 13.04.1961 : junior lecturer in history of philosophy of the Middle Ages at the Université libre de Bruxelles.
• 15.10.1964 : resigns at the Royal Library.
• 07.07.1967 : co-founder and chairman of the Centre International de Codicologie, initially Centre de Codicologie.
• 1968-1970 : professor at the Faculty of Literature and Humanities of the Université de Lille.
• 12.09.1979 : died in Schaerbeek (Brussels).

"On a theoretical level he is one of those who made numerous efforts to turn codicology into an autonomous science " (Pierre Jodogne, " François Masai, codicologue ", in Miscellanea Codicologica F. Masai, Dicata MCMLXXIX, Ghent, E. Story-Scientia, 1979, vol. I, p. XLIX.), as well as to establish a clear distinction between this codicology, the archaeology of books and fields such as paleography, epigraphy, papyrology, diplomatics etc. As a professor in the history of the Middle Ages, the history of Byzantium and the history of christianity, as a specialist in monachism and a member of the board of directors of the review Byzantion, he forced himself " not to dissociate the history of ideas from the history of the texts expressing those ideas ". In co-operation with Martin Wittek he supervised the execution and guaranteed the publication of the catalogues of dated manuscripts preserved in Belgium (1968-1972). In 1959 he had encouraged Martin Wittek to create the Bulletin codicologique which he associated with Scriptorium.

Portrait : unknown photographer (DR).