Significance Particles of all shapes and sizes flowing through tight spaces are ever present in applications across length scales ranging from blood flow through tissue capillaries to industrial-scale processes. To date, separating these particles relies on methods employing external force fields. Currently underexplored, omnipresent fluid–structure interactions hold the key to shape-based separation independent of external intervention. By leveraging experiments, theory, and simulations, we show how the symmetry of a particle determines its overall trajectory: In particular, mirror-symmetric particles, both strongly and weakly confined, follow a universal path. We propose minimalistic scaling relations to describe how particle shape affects the parameterization of the universal path. These findings could be used to “program” particle trajectories in lab-on-a-chip devices and industrial separation processes.