Abstract: In modern EFTs, field redefinitions are a commonly used tool to change bases and simplify calculations, though typical redefinitions often assume some minimum properties such as locality. This leads to a natural question -- what field redefinitions are allowed? In this talk, I will revisit this lore and demonstrate that there are essentially no restrictions. Field redefinitions may be symmetry-breaking, non-local, or even have explicit spacetime dependence. I will discuss both the perturbative case and the more subtle case where changes are resummed into the definition of the propagator with an eye towards correlation functions and S-matrix elements.