• Remote sensing data, TROPOMI and AHI were used to quantify lockdown impact. • NO2 experienced the highest decrease in East Asia due to lockdowns. • NO2 (83%) and SO2 (71%) decreased more than HCHO (11%) and CO (4%) in Wuhan. • SO2 increased in Seoul and Tokyo due to polluted air transport in 2020. • HCHO to NO2 ratio increased from below 1 to above 2 in East China in February 2020.