In this paper, we investigate the question of whether a typical vector field on a compact connected Riemannian manifold M d has a "small" centralizer. In the C 1 case, we give two criteria, one of which is C 1 -generic, which guarantees that the centralizer of a C 1 -generic vector field is indeed small, namely collinear. The other criterion states that a C 1 separating flow has a collinear C 1 -centralizer. When all the singularities are hyperbolic, we prove that the collinearity property can actually be promoted to a stronger one, refered as quasi-triviality. In particular, the C 1 -centralizer of a C 1 -generic vector field is quasi-trivial. In certain cases, we obtain the triviality of the centralizer of a C 1 -generic vector field, which includes C 1 -generic Axiom A (or sectional Axiom A) vector fields and C 1 -generic vector fields with countably many chain recurrent classes. For sufficiently regular vector fields, we also obtain various criteria which ensure that the centralizer is trivial (as small as it can be), and we show that in higher regularity, collinearity and triviality of the C d -centralizer are equivalent properties for a generic vector field in the C d topology. We also obtain that in the non-uniformly hyperbolic scenario, with regularity C 2 , the C 1 -centralizer is trivial. 9 4. Quasi-triviality 13 4.1. Collinear does not imply quasi-trivial 13 4.2. The case of hyperbolic zeros 13 5. The study of invariant functions and trivial centralizers 18 5.1. First integrals and trivial C 1 -centralizers 19 5.2. Some results in higher regularity 20 6. The generic case 23 Appendix A. The separating property is not generic 40 References