Bitnodes, a website and data store designed to track the ebb and flow of full nodes in the Bitcoin network, is a project by Addy Yeow. Originally, the Bitnodes service was supported by the Bitcoin Foundation, an organization looking to promote and standardize Bitcoin use; but as of October 4, 2015 that appears to have changed to 21.co, the domain supported by Bitcoin mining and device company 21, Inc.

A full node is a computer or device in the Bitcoin network that enforces all the rules of the Bitcoin network and serves a full copy of the Bitcoin blockchain, which is the globally distributed ledger of every transaction executed on the network. Full nodes make up the backbone of the Bitcoin network and act to provide fidelity to the consensus rules of Bitcoin that provide security to transactions.

The news of the change appeared discreetly in a GitHub update from Yeow related to the project.

Bitnodes provides a map of the world that visualizes the size of the Bitcoin network and it does so by finding all of the reachable nodes on the network.

From the site:

The current methodology involves sending getaddr messages recursively to find all the reachable nodes in the network, starting from a set of seed nodes. Bitnodes uses Bitcoin protocol version 70001 (i.e. >= /Satoshi:0.8.x/), so nodes running an older protocol version will be skipped. The crawler implementation in Python is available from GitHub (ayeowch/bitnodes) and the crawler deployment is documented in Provisioning Bitcoin Network Crawler.

The shift to support under 21, Inc. from the Bitcoin Foundation follows news that the Foundation was having monetary troubles in April of this year.

21, Inc. also recently released details of a small device capable of running a Bitcoin node known as the 21 Bitcoin Computer slated to ship November 16. The computer includes hardware and an API designed to allow developers to create apps that would use the Bitcoin network and join it as a marketplace for Internet of Things devices.

Featured image credit: Bitnodes.21.co website screenshot