The emerging technical possibilities of cinema in the digital age – such as the use of CGI and, more recently, generative AI and its deepfake capabilities – invite us to revisit the classic problem of documentary and its relationship with realism. In light of the new historical framework of cinema, the ontological specificity of the concept of documentary is now subject to renewed ethical and aesthetic considerations. Based on the analysis of some recent examples of documentary cinema – such as Prehistoric Planet, In Event of Moon Disaster and Roadrunner – this article focuses on the relationship between realism and performativity to determine how different forms of realism coexist in documentaries, simultaneously feeding both their ethical-epistemological function and their aesthetic dimension. One of the conclusions put forward in this article is that the ethical questioning of documentary film is inseparable from the theoretical problem of its delimitation as a genre. Describing the particular type of realism that governs the documentary is essentially the same as describing its ethical foundations. And this becomes even more evident in the age of AI.