A full-scale Russian invasion against Ukraine has triggered the largest humanitarian migration in Europe since the World War II. Since the start of the war up until January 2023, almost 6 million Ukrainians have resettled within Ukraine and almost 8 million sought protection in neighboring and more distant countries. Do Ukrainians who stayed in Ukraine differ from those who went abroad in terms of demographic and socio-economic characteristics, visions of the future, attitudes, and experiences in coping with the war situation? What guides their decisions on whether to stay or leave their home? How Ukrainian IDPs and refugees adapt to the new environment and whether they plan to return home? Are refugees’ first steps in the host countries successful and how their integration in the labour market, education and training system and social life differs across the countries? To answer these and related question the Online Survey of Ukrainians (OneUA) approaches three groups of Ukrainians: (1) those, who stayed at home in Ukraine, (2) those who moved within Ukraine (i.e., internally displaced persons, IDPs) and (3) those who left Ukraine as refugees for the following countries: Poland, Germany, Czech Republic, Hungary, Italy, Moldova, the Netherlands, and Romania. We invite users of Facebook, Instagram and Facebook Messenger, who are 18+ years old, who identify themselves as Ukrainians and who resided in Ukraine on February 23, 2022 to participate in an online survey and answer a set of questions related to the following topics: (a) migrations decisions and settlement patterns, (b) labour market and economic situation, (c) social and cultural adaptation. Two waves of the survey tracing the same respondents across time and destinations are planned.