Over half of the world’s population is at least bilingual. The construct of bilingualism is dynamic and fluid, which is to say, not all bilingualism is the same. Consider the fact that the label “bilingual” itself encompasses a diverse array of types, from simultaneous child acquirers in bilingual societies, to late adult second-language learners in and outside of linguistic immersion, to minority (heritage) language speakers growing up in societal monolingualism and many more contexts. With the important differences that pertain to context, opportunities for engagement with the experiences of bilingualism that ultimately lead to linguistic, cognitive, neurological and social outcomes vary across a wide range of dimensions for bilingual types in general, specific groups and, of course, individuals. Indeed, research has shown that age of onset, duration of bilingualism, intensity and degree of usage (in real and apparent time), (shifts) in linguistic dominance (over time), exposure to/training in literacy, variation in input (quantity and quality), social networks for language use, sociopolitical contexts amongst other co-varying factors weigh differentially on how the processes of bilingualism unfold. In this light, recent years have witnessed major shifts away from traditional categorical treatments of bilingualism, seeking to unpack the determinants of the wide range of individual variation. This issue of Applied Psycholinguistics is dedicated to the fascinating, yet puzzling and challenging task of teasing out, quantifying, modelling and predicting those individual differences to systematically map experiences to outcomes. The papers collected herein are the keynote addresses and some selected talks from the workshop Capturing and Quantifying Individual Differences in Bilingualism, which gathered experts from the fields of linguistics, psychology and cognitive neuroscience in September 2019 at UiT The Arctic University of Norway in Tromsø. Together, they provide an impressive coverage of the bilingualism experience, from basic epistemology to detailed methodology and constitute an invaluable reference point and roadmap for anyone interested in what capturing and quantifying all things bilingualism as a continuum entails.