The Determinants of Social Connectedness in Europe -- Combining Language Models and Network Features for Relevance-based Tweet Classification -- Co-Spread of Misinformation and Fact-Checking Content during the Covid-19 Pandemic -- Facebook Ads: Politics of Migration in Italy -- It's Not Just About Sad Songs: The Effect of Depression on Posting Lyrics and Quotes -- Understanding The MeToo Movement Through The Lens Of The Twitter -- Discovering Daily POI Exploitation using a LTECell Tower Access Trace in Urban Environment -- Identifying the Hierarchical Influence Structure Behind Smart Sanctions Using Network Analysis -- Coverage and Evolution of Cancer and its Risk Factors - A quantitative study with Social Signals and Web-Data -- Detecting Engagement Bots on Social Influencer Marketing -- Social Capital as Engagement and Belief Revision -- Employee Satisfaction in Online Reviews -- Stable Community Structures and Social Exclusion -- Inside the x-rated world of "premium" social media accounts -- Impact of Online Health Awareness Campaign: Case of National Eating Disorders Association -- Moral Framing and Ideological Bias of News -- Malicious Bot Detection in Online Social Networks: Arming Handcrafted Features with Deep Learning -- Spam Detection on Arabic Twitter -- Beyond Groups: Uncovering Dynamic Communities on the WhatsApp Network of Information Dissemination -- Structural invariants in individuals language use: the "ego network" of words -- Dynamics of scientific collaboration networks due to academic migrations -- Social Search and Task-related Relevance Dimensions in Microblogging Sites.-Regional Influences on Tourists Mobility Through the Lens of Social Sensing.-Genuine Personal Identifiers and Mutual Sureties for Sybil-Resilient Community Growth -- Political Framing: US COVID19 Blame Game -- Measuring adolescents' well-being: correspondence of naïve digital traces to survey data -- A Computational Analysis of Polarization on Indian and Pakistani Social Media -- Young Adult Unemployment Through the Lens of Social Media: Italy as a Case Study -- Women worry about family, men about the economy: Gender differences in emotional responses to COVID19 -- Jump on the Bandwagon? Characterizing Bandwagon Phenomenon in Online NBA Fan Communities -- ALONE: A Dataset for Toxic Behavior among Adolescents on Twitter -- Cross-domain Classification of Facial Appearance of Leaders -- The Effect of Structural Affinity on the Diffusion of a Transnational Online Movement: the Case of #MeToo. .

This volume constitutes the proceedings of the 12th International Conference on Social Informatics, SocInfo 2020, held in Pisa, Italy, in October 2020. The 30 full and 3 short papers presented in these proceedings were carefully reviewed and selected from 99 submissions. The papers presented in this volume cover a broad range of topics, ranging from works that ground information-system design on social concepts, to papers that analyze complex social systems using computational methods, or explore socio-technical systems using social sciences methods.