  We solve a long-standing puzzle in Statistical Mechanics of disordered
systems. By performing a high-statistics simulation of the D=3 random-field
Ising model at zero temperature for different shapes of the random-field
distribution, we show that the model is ruled by a single universality class.
We compute the complete set of critical exponents for this class, including the
correction-to-scaling exponent, and we show, to high numerical accuracy, that
scaling is described by two independent exponents. Discrepancies with previous
works are explained in terms of strong scaling corrections.
