The function of ARHGAP31 (Rho GTPase activating protein 31, Ensembl gene identifier ENSG00000031081) is as follows. Functions as a GTPase-activating protein (GAP) for RAC1 and CDC42. Required for cell spreading, polarized lamellipodia formation and cell migration. {ECO:0000269|PubMed:12192056, ECO:0000269|PubMed:16519628}.