General sources

Archive.org, a true memory of the Internet (www.archive.org)

Archives de littérature du Moyen Âge (Arlima) (http://www.arlima.net/)

Diplomata Belgica. The Diplomatic Sources from the Medieval Southern Low Countries (http://www.diplomata-belgica.be/colophon_en.html) 

Duke Papyrus Archive, papyrology resources (http://library.duke.edu/rubenstein/scriptorium/papyrus/)

Fathers of the Church, anthology of works, in English (https://www.newadvent.org/fathers/)

Gallica, bibliothèque numérique de la BNF (gallica.bnf.fr/)

Mandragore, base iconographique du département des mss de la BNF (mandragore.bnf.fr/html/accueil.html)

Mirabile. Digital Archives for Medieval Culture (https://mdl.mirabileweb.it/list)

Monumenta Germaniae Historica online (www.dmgh.de/) 

Relmin. Publication and study of legal texts defining the status of religious minorities in medieval Europe (https://telma.irht.cnrs.fr/outils/relmin/index/)