This chapter discusses some of the opportunities offered by Big Data to understand mobility practices. However, beyond its promises, it has to be considered as human and social constructions. Therefore, the author underlines the importance of describing all the decisions, operations, constraints, etc. that shape these data and the algorithms they feed in order to identify their limitations. This chapter also points out the challenges of Big Data for scientific research, in terms of the opportunities it offers to renew the understanding of mobility, but also the challenges it poses for the human and social sciences (HSS)