This article sheds light on how adults in Barcelona (ES), Groningen (NL), and Milan (IT) utilized WhatsApp to compensate for the lack of face-to-face interactions and to fight social isolation during the first 2 months of the COVID-19 lockdown. We argue that practices of WhatsApp usage have multiplied and diversified experiences of co-presence at distance and made group socialities even more important than before. Building on the concepts of “scalable socialities” and “polymedia,” the article formulates the concept of “scalable co-presence” to account for ways in which WhatsApp has enabled multiple experiences of proximity to others across different scales of sociality, from one-to-one to large groups interactions. In this article, we also argue that the concept of “scalable co-presence” is relevant to bring the study of mediated co-presence out of media and migration studies into the broader field of media and cultural studies. With reduction in mobility, increased social distancing, and ubiquitous connectivity, the role of communication technologies in mediating proximity at distance has become crucial for many more people around the world outside the context of transnational migration. The concept is also relevant to acknowledge the increased importance of mediated group interactions and communications in (post)-pandemic digital societies.