CODECS is a collaborative web platform which draws heavily on data management technologies from Semantic MediaWiki and its spin-offs to accommodate resources for the benefit of scholars of Celtic studies worldwide. By far its most ambitious ongoing project is the *selgā catalogue, a research and teaching tool focusing on annotated descriptions of historical sources (texts and manuscripts) and bibliographic records, with well over 15,000 entries and counting. Also of special note is Tionscadal na Nod, which serves as an aid to interpreting abbreviations and other devices employed by scribes of vernacular Irish manuscripts.