Field-induced domain wall (DW) propagation was evidenced in unpatterned layers of in-plane magnetized Ga1−xMnxAs1−yPy using Kerr microscopy. Both stationary and precessional regimes were observed, and domain wall velocities of up to 500 m s −1 were measured, of the order of magnitude of those observed on in-plane magnetized metals. Taking advantage of the strain-dependent magneto-crystalline anisotropy in this dilute magnetic semiconductor, both out-of-plane and in-plane anisotropies were adjusted by varying the manganese and phosphorus concentrations. We demonstrate that these anisotropies are a critical parameter to obtain large velocities. These results are interpreted in the framework of the one-dimensional model for domain wall propagation.