In this chapter, Gijsbert Rutten, Iris Van de Voorde and Rik Vosters, refine the Labovian distinction based primarily on the type of language learning involved by bringing in the contact-based insights of Milroy (2007) on this issue. Exploring the extent to which the transmission-diffusion distinction can also apply to orthographic, rather than phonological or morphosyntactic, changes, the authors discuss a range of different examples of both transmission and – various subtypes of – diffusion, mostly from Dutch, German and English. Their central argument is that diffusion must be seen as the dominant driver of orthographic change, but transmission-type changes are also possible in specific historical contexts, for instance in relation to explicit instruction in schools or in closely-knit social networks. Building on different examples and cases, the chapter also explains the link between diffusion and supralocalization, as local and regional spelling practices in medieval times give way to more supraregional writing traditions in postmedieval times. As such, these processes of geographical diffusion of innovations across communities often lay the ground work for later standardization efforts. However, by discussing a slightly more elaborate case study on spelling change and pluricentricity in Dutch language history, the authors show how the development of such supraregional writing traditions often leads not only to linguistic standardization, but also results in a linguistic landscape which can best be described as pluricentric, consisting of different national and regional normative centers from which innovations spread.