Prosopography has been used as an analytical tool by historians for about 150 years, with increasing energy. The great print volumes of the 20th century are gradually being transformed into the digital resources of the 21st century. Working with one such project, the Prosopography of the Byzantine World (https://pbw2016.kdl.kcl.ac.uk/) has been very instructive; we have learned, gradually, to discard the structure imposed by the printed book, and engage fully with the new medium. One lesson is that the limitations on what is included have to be made crystal clear – since there are no limitations imposed by space, everyone must indicate the precise criteria for their selections. This can make the prospect rather scary; but the most exciting aspect is that working in this way allows new kinds of collaboration. The only requirement is a confirmed identifier: using this, data and ideas presented by many scholars can be linked and cross-referred to one another, while each scholar retains credit – and responsibility – for their own work. The concept is a traditional one in the humanities: these are dynamic footnotes. All of this is very new, and at present we are all establishing the parameters and the protocols. The prosopography of the Late Antique period – with many publications, both on paper and online, and many categories of organisation: secular/ecclesiastical/military/regional/ – offers us an important opportunity to explore how a series of very different publications, each with a distinct editorial flavours can develop a dynamic and productive interchange of ideas.