Although each person is unique in the world, the first and last names are not. That is why we can find people with the same name anywhere on the planet and also people with whom we share a surname. This, precisely, is what allows Forebears, a website where we can find who has our same surname and find out where they live, thanks to a map that contains the 11 million surnames registered on the web.
To create this registry, the Forebears developers have been collecting data in newspapers, genealogy websites and other similar sources, both free and paid since 2012. In addition to how many people have the same surname as a user and the places where they live, the web allows to know other data related to the surname, such as the meaning, places where it is more abundant, war records, burials, census, etc.
As for the most common surnames in each country, Forebears indicates that Smith, Johnson, Williams, Jones, Brown, Davis, Miller and Wilson are the most popular surnames in the United States.
However, in some countries such as Vietnam the information is not complete, so sometimes, and depending on the country, it is unreliable.