These files contain data supporting all results reported in Van Linn et al. 2026, "Precursory slow-slip fronts navigate sticky spots and then initiate faster sliding on the Whillans Ice Plain". Slow-slip sometimes precedes earthquakes, landslides, and other interfacial sliding events. We study the 2D propagation of precursory slow-slip fronts and their interaction with heterogeneous interfacial properties by using the Whillans Ice Plain (WIP) in West Antarctica as a natural study-system. The WIP slips with distinct stick-slip motion; ~0.5m of slip occurs in 30-minute episodes every 8-25 hours with little displacement between events. Using GNSS data from 20 stations placed on the WIP in a 60-km array, we mapped the migration of slow-slip fronts that preceded faster widespread sliding events. The fronts propagate with velocities of 15 – 100 m/s, travel slower across highly coupled “sticky spots”, and then accelerate to 100-240 m/s once the highly coupled spots are traversed. Considering only eventto-event variation, precursor front velocity increases with increasing inferred local basal shear stress. The effect of sticky spots on rupture propagation is similar to that of high normal stress bumps in recent laboratory experiments. They can both slow down ruptures and act as sites of slip acceleration. The comparison suggests that the mechanics that underlie interactions between a rupture front and a bump can be similar on the cm and km scale. However, slip events on the WIP likely result from ~6 kPa stress drops, orders of magnitude smaller than most tectonic environments. Thus, the behavior observed at the 10 km scale on WIP likely occurs at far larger temporal and spatial scales than on tectonic faults during earthquake nucleation.