The map on Cancheng Li’s academic homepage shows one red dot for each distinct public IP recorded by this service. People sharing a public IP share one dot; a changing IP may create another dot.
Locations are approximate. A proxy or VPN is located at its public exit. Same-city dots are spaced apart for readability and do not show street addresses. Visits without a city location are counted separately.
The application stores a keyed hash instead of the raw IP, alongside an approximate city location. Public map responses contain city counts only. IP and location are obtained at the hosting edge, without a separate browser geolocation service.