RegioSQM20 predicts the regioselectivity of EASs by finding the reaction center with the highest proton affinity. For computational efficiency the proton affinities are computed using the semiempirical tight binding method GFN1-xTB and a continuum solvent model of methanol. The centers with proton affinities within 1 kcal/mol of the maximum are considered reactive. The method thus has only a handful of hyperparameters (choice of computational method, solvent, energy cutoff, conformational search method) and these are chosen based on a dataset of 532 experimental measurements, some of which are included in the current training set.