The Bitnodes website aims to gather information on Bitcoin nodes to estimate the size of the network. The website is very straightforward and easy to navigate. It displays a live map of the world showing the concentration on Bitcoin nodes across different countries. There is also a table showing nodes per country and which country has the most nodes in volume and percentage terms.
There is also information which explains the methodology through which Bitnodes arrives at its figures. Older nodes than protocol version 70001 will be skipped. The methodology involves sending messages to getaddr reachable nodes to estimate the size of the network. The code for the implementation is also available on GitHub.
Bitnodes is supported by Earn.com. Earn.com, rebranded from 21.co, enables users to earn digital cryptocurrency by answering emails.