We show that the Proca equation in vacuum, as well its plausible modifications dielectric media, is incompatible with experimental evidence, no matter how small mass is.Received 18 March 2022Revised 21 December 2022Accepted 6 February 2023DOI:https://doi.org/10.1103/PhysRevD.107.056013© 2023 American Physical SocietyPhysics Subject Headings (PhySH)PropertiesMassParticles & Fields