This chapter clarifies that the treatment and reliability of orthographic variables as linguistic variables has already been tested with the application of both macroscopic and microscopic approaches to digitalized historical materials. Patterns of variation and change in past periods of a given language have been evidenced through the observation of its users’ sociolinguistic behavior in social interaction. The recent prolific research output in historical sociolinguistics reflects the growth of interest in style and register within the field. The role of new genres and text types (e.g. travel accounts, court records, recipes, diaries, and letters) is thus also being highlighted as materials worth studying for both interspeaker and intraspeaker variation. The chapter explores the indexical potential of orthographic variation in style, register, genre and text types. The extralinguistic factors conditioning the use of different spelling forms in cases of variability are usually based on production, geographical location, sociodemographics (sex, age, rank), social networks, text type (and genre), style, register and medium (handwritten vs. printed). In earlier periods, when correspondence and other ego-documents were probably the most frequent means of written communication and without the existence of a well-established and fixed standard variety, orthographic variation constituted a source of social meaning.