This innovative collectionadvances the notion of social media materialities to draw attention to the ways in which physical aspects steer contentious practices and, inversely, how technologies and economic models are handled and performed by users.

Mette Mortensen is Associate Professor at the University of Copenhagen, Denmark. She is the Principal Investigator of the collective research project "Images of Conflict, Conflicting Images" (2017-2021) and author or editor of seven books, including Eyewitness Images and Journalism (2015).

Christina Neumayer is Associate Professor at the IT University of Copenhagen. Her research focusses on the role of media technologies in political conflict. She has published on digital media and activism, social movements, racism, and propaganda.

Thomas Poell is Senior Lecturer at the University of Amsterdam, the Netherlands. His research focuses on digital platforms and public communication. He co-authored The Platform Society (2018), and co-edited Global Cultures of Contestation (2017) and The Sage Handbook of Social Media (2018).

Introduction: Social media materialities and protest Christina Neumayer, Mette Mortensen and Thomas Poell

PART I: Spatiality

I post, you rally, she tweets... and we all occupy: The challenges of hybrid spatiality in the Occupy Wall Street mobilizations Alice Mattoni

Rethinking networked solidarity Sky Croeser

Nomads of cyber-urban Space: Media hybridity as resistance Emiliano Treré

PART II: Temporality

(Social) media time, connective memory and activist television histories: The case of TV Stop (1987-2005) Tina Askanius

Facebook's communication protocols, algorithmic filters, and protest: A critical socio-technical perspective Lorenzo Coretti and Daniele Pica

Social media as activist archives Christina Neumayer and David M. Struthers

PART III: Platformization

Theorizing civic engagement and social media: The case of the "refugee crisis" and volunteer organising in Sweden Julie Uldam and Anne Kaun

The materiality of clouds: Beyond a platform-specific critique of contemporary activism Stefania Milan

"Please leave my news feed alone": Exploring user protest against algorithmic personalization Martina Skrubbeltrang Mahnke

Evolving digital repertoires of contention in transitional societies: The case of China Jun Liu

Afterword: Lessons and puzzles in studying social media materialities and protest Alexandra Segerberg and W. Lance Bennett