Mass-loss rate as a function of stellar luminosity for the analyzed SMC OB stars with available UV data. Luminosity classes are distinguished by different symbols as given in the legend. A power-law fit to the empiric relation is represented by the blue solid line. For comparison, we include the empirical relation for LMC OB stars (Ramachandran et al. 2018a) along with theoretical predictions (Vink et al. 2001) (dotted lines) at SMC and LMC metallicities. The empirical relations for WN stars in the SMC and LMC (Hainich et al. 2017) are also illustrated in the plot (dashed lines).