Freedom of movement is a prime ambition of European integration, allowing citizens to freely live, study, and work in other states, even beyond the borders of the European Union (EU), e.g. in Switzerland. It is also subject to political controversy, as shown by the Swiss limitation initiative, or Brexit. Particularly access to social benefits for mobile EU citizens in host countries has sparked political conflict. This project analyses bureaucratic discrimination – the biased treatment of different EU citizens by frontline bureaucrats – within this context. We ask three questions: Is bureaucratic discrimination against different types of mobile EU citizens, who try to access social benefits, mainly a reflection of societal discrimination (RQ1), or do national administrative contexts influence patterns of bureaucratic discrimination (RQ2)? And how can bureaucratic discrimination within different contexts be overcome (RQ3)?Administrative behaviour plays an important – but understudied – role for freedom of movement. First, member states may introduce administrative burdens that limit non-nationals’ access to social benefits to resolve the tension between commitments regarding EU citizenship and domestic political conflict over alleged ‘welfare tourism’. Second, the legal conditions under which mobile EU citizens have access to social benefits abroad are so complex that support in navigating foreign administrative systems is almost indispensable for exercising their social rights. Bureaucratic discrimination thus becomes particularly consequential. Behavioural public administration research has highlighted the attributes that can trigger bureaucratic discrimination based on micro-level cognitive mechanisms. Unfortunately, the role of national administrative contexts is poorly understood; both in affecting bureaucratic discrimination and in influencing the effectiveness of anti-discrimination measures. One main reason for this is that cross-national experiments – prominent within economics – have not yet fertilized public administration research. Our project innovates by unravelling the national scope conditions of bureaucratic discrimination through cross-national experiments that are complemented with qualitative evidence. Module 1 analyses all three RQs through survey-based conjoint experiments with the general public and bureaucrats in four countries with different national bureaucratic models: Spain (Southern Napoleonic), Denmark (Nordic), Ireland (Anglo-Saxon), and Switzerland (Federal). By comparing group differences of discrimination (general population vs. bureaucrats) across countries, we analyse whether bureaucratic discrimination is indistinct from societal discrimination or influenced by national bureaucratic cultures, and how this affects the effectiveness of anti-discrimination measures. Module 2 evaluates the external validity of these results by moving into the field to conduct experiments with consenting frontline bureaucrats in welfare offices in all four countries (RQ2-3). Module 3 adopts a qualitative approach to probe the internal and external validity of these findings by using in-depth vignette-based interviews with frontline bureaucrats in Switzerland and Spain (RQ2-3). This way, the project advances public administration and mobility research by analysing national administrative contexts as potential scope conditions for the extent of bureaucratic discrimination and for how well anti-discrimination measures work.