The COVID-19 pandemic has had a rapid and significant impact on mobility. One of the most important responses of countries worldwide to slow the spread of the pandemic is to restrict the movement of people, which has had a considerable effect on transport systems. However, the reduction of transport is not identical for all modes of transport: public transport has seen the greatest decline so far. Understanding urban modal share developments during a pandemic situation can help cities better prepare for transport management in the future. •COVID-19 measures decreased mobility by half in Budapest, Hungary.•Modal share of public transport decreased dramatically due to COVID-19 measures.•Car usage increased to 65% from 43% in the modal share.•Bicycle usage saw the greatest growth rate by more than doubling its share in the modal share.•Bike sharing became more popular due to rapid measure, other mobility sharing systems saw lower than average decrease.