This talk discusses recent developments in the use of social media platforms as a source of data, and as a tool for survey research, in order to improve our understanding of migration and population health, and to support policy decisions. It concentrates on two main components: (i) the use of Facebook data to measure migration and mobility in the aftermath of natural disasters; (ii) the use of Facebook as a tool for survey research, with a focus on methods and initial results for the Covid-19 Health Behavior Survey (CHBS). CHBS is an online survey that was conducted by the Max Planck Institute for Demographic Research daily from Mar. 13 to Aug. 12, 2020, resulting in approximately 144,000 completed questionnaires across eight countries in Europe and North America. The survey relied on participant recruitment via targeted advertisement and collected information on people’s health, attitudes, behaviors, and social contacts relevant for understanding how people responded to Covid-19 and to physical distancing guidelines.