  We implement the effects of disorder on a holographic superconductor by
introducing a random chemical potential on the boundary. We demonstrate
explicitly that increasing disorder leads to the formation of islands where the
superconducting order is enhanced and subsequently to the transition to a
metal. We study the behavior of the superfluid density and of the conductivity
as a function of the strength of disorder. We find explanations for various
marked features in the conductivities in terms of hydrodynamic quasi-normal
modes of the holographic superconductors. These identifications plus a
particular disorder-dependent spectral weight shift in the conductivity point
to a signature of the Higgs mode in the context of disordered holographic
superconductors. We observe that the behavior of the order parameter close to
the transition is not mean-field type as in the clean case, rather we find
robust agreement with $\exp(- A\, |T-T_c|^{-\nu})$, with $\nu =1.03\pm 0.02 $
for this disorder-driven smeared transition.
