  We study the effect of long range dipolar forces on the dynamics and
morphology of domain walls in magnetic thin films by numerical simulations of
the spin-1 random field Ising model. By studying the size distribution of
avalanches of domain wall motion arising as a response to quasistatic external
driving, we observe a cross-over from the case dominated by short range
interactions to another universality class where the long range dipolar forces
become important. This crossover is accompanied with a change of the domain
wall morphology from a rough wall to walls with zigzag structure.
