During the first wave of Covid in Russia it appeared that Yandex could measure the city activity level by comparing trends of how people were using its services before and during the pandemic. This discovery enabled creation of the Self-Isolation Index – a 0 to 5 grade scale, based on the anonymous data from 24 Yandex apps, used daily by 60% of Russians. The Index was measured live for 173 cities with over 100k citizens and placed on the most visited web page in Russia.