Chapter 9 discusses the relationship between transmission, diffusion and orthography. While diffusion can be seen as a more dominant driver of orthographic change, changes induced by transmission are also possible in some historical scenarios, for example through formal instruction or via closely knit social networks. Drawing on a number of examples from previous studies, the chapter also engages with supralocalisation, intended as an antecedent to standardisation, as local and regional orthographic conventions in the pre-standardisation era give way to more supraregional writing traditions. Thus, instances of geographical diffusion across communities frequently provide essential groundwork for later standardisation initiatives. The chapter ends with a reference to the importance of including pluricentricity in our understanding of standardisation. It is by studying regional writing traditions that one can trace the formation of a standard not as an exclusive national form, but rather as a pluricentric scenario. In the development of many European pluricentric orthographies, not least German and French, some writing traditions eventually became part of the overall profile of the regional influence through diffusion, while still not becoming a uniform fixed set of shibboleths for the whole geographical area.