This chapter reviews the transformative effects of technology on dictionary-making, focusing on four main areas: the use of databases for storing and organising dictionary text; the creation and exploitation of corpora for use as the dictionary’s evidence base; the enhancement of the value and usability of corpus data through the application of software tools developed in the NLP (natural language processing) community; and the migration of dictionaries from print to online media. During the last half-century, activity in all these areas has brought fundamental changes to the way dictionaries are created and made available to their users. We trace the development of corpus-based lexicography in English, from the early work of John Sinclair and his colleagues in the 1980s to the present day. Lexicographers working in English and other widely used languages now have access to resources which would scarcely have been imaginable thirty years ago: very large corpora (measured in tens of billions of words) and sophisticated corpus-querying tools are routinely available. The move from print to digital publication is a more recent development, but no less significant. The far-reaching implications of these changes – for dictionary-makers and dictionary-users alike – are explored at every stage.