Integration is becoming increasingly important in law, due to the growing involvement of the legislative, executive and judicial powers at European, national, regional and local levels. This phenomenon concerns third-country nationals and EU citizens, despite the fundamentally different legal regimes applicable to these groups. In this article, I discuss the expansion of integration duties and the different legal mechanisms which they are based on. I propose four conditions- and obligations-based integration models likely to be found in EU law and national laws: the symbolic model, the meritocratic model, the activation model and the selective model. From a legal perspective, identifying these integration mechanisms is essential for assessing compliance with fundamental rights and EU law. Moreover, such a typology is likely to help researchers, policy-makers and the public obtain a better sense of how the conception of integration evolves in our societies and in the legal field in particular. I conclude by briefly sketching a common trend which I observed throughout the four models: they are imbued with a strong socioeconomic dimension hindering the socioeconomically underprivileged categories.