  We show that the coherent forward scattering (CFS) interference peak
amplitude sharply jumps from zero to a finite value upon crossing a
metal-insulator transition. Extensive numerical simulations reveal that the CFS
peak contrast obeys the one-parameter scaling hypothesis and gives access to
the critical exponents of the transition. We also discover that the critical
CFS peak directly controls the spectral compressibility at the transition where
eigenfunctions are multifractal, and we demonstrate the universality of this
property with respect to various types of disorder.
