Node

A node is a computer that runs blockchain software and connects to other computers doing the same, together forming the peer-to-peer network that keeps a blockchain running. Each node relays transactions and blocks to its peers, checks that incoming data follows the network's rules, and stores some or all of the chain's history. Because thousands of independent nodes hold the same data, no single company or server outage can take the network offline or quietly rewrite its records.

Nodes come in several flavors. Full nodes verify every transaction and block against the consensus rules. Light clients store only block headers and rely on full nodes for details. Mining or validator nodes additionally produce new blocks. For example, anyone with a spare computer and enough disk space can download Bitcoin Core, let it sync the chain's history, and from then on independently verify every bitcoin transaction without trusting an exchange or block explorer.

A common misconception is that running a node earns you cryptocurrency; ordinary nodes receive no rewards — only miners or validators do — and people run them for verification, privacy, and to support the network. The number and geographic spread of independent nodes is one of the most cited measures of how decentralized a blockchain really is, since a network whose nodes are few or concentrated in one data center is easier to censor or control.