Standard Model anomaly cancellation

In each Standard Model generation, quark and lepton hypercharges cancel the $SU(3{)}_c^3$, $SU(3{)}_c^{2}U(1{)}_Y$, $SU(2{)}_L^{2}U(1{)}_Y$, $U(1{)}_Y^3$, and mixed gauge-gravitational anomalies. The four left-handed $SU(2{)}_L$ doublets also avoid the global Witten anomaly.