By-now photons are the unique universal messengers.Cosmological sources like far-away galaxies or quasars are well-known light-emitters.Here we demonstrate that the nonlinear electrodynamics (NLED) description of photon propagation through the weak background intergalactic magnetic fields modifies in a fundamental way the cosmological redshift, z, that a direct computation within a specific cosmological model can abscribe to a distant source.Independently of the class of NLED Lagrangian, the effective redshift turns out to be (1 + z)| eff = (1 + z) ∆, where ∆ ≡ (1 + Φ e )/(1 + Φ o ), with Φ ≡ 8/3(L FF /L F )B 2 , being L F = dL/dF, L FF = d 2 L/dF 2 , the field F ≡ F αβ F αβ , and B the magnetic field strength.Thus the effective redshift is always much lower than the standard redshift, but it recovers such limit when the NLED correction ∆(Φ e , Φ o ) -→ 1.Therefore, once that we do not actually ever observe proper distances, then one can argue that for a particular redshift the observed luminosity distance of the light-emitting far-away source is different.The observational implications of this peculiar result are discussed.