ASAP2f is a genetically encoded fluorescent voltage indicator that can report rapid changes in neural activity. It was generated by introducing amino acid substitution A147S and deleting amino acid residue A148 from ASAP1. ASAP2f produces larger fluorescence changes (for both depolarization and hyperpolarization) compared to ASAP1, with similar response kinetics (FBrf0232743). For detailed kinetic and spectral properties and a comparison of ASAP2f with other fluorescent voltage indicators, see FBrf0232743.