Node

A Bitcoin node is a computer running Bitcoin software that participates in the peer-to-peer network. It receives transactions and blocks, validates them against the consensus rules, and relays valid ones to its peers.

Nodes come in two practical flavors:

• Full nodes download and validate every block from the genesis block onward, maintaining the complete UTXO set and enforcing every consensus rule independently. This is the gold standard of trustlessness.
• SPV (Simplified Payment Verification) nodes download only block headers and rely on full nodes to confirm transaction inclusion via Merkle proofs. They're much lighter. Each block header is 80 bytes, about 4.2 MB a year, so the headers for the roughly 970,000 blocks mined by October 2026 come to about 78 MB. Bitcoin Core 31's setup screen, by contrast, says a full node will store at least 870 GB. The catch is that SPV nodes give up some verification guarantees.

Nodes are how Bitcoin enforces its rules. Miners propose blocks; nodes accept or reject them. A miner that produces an invalid block - too much subsidy, an invalid signature, a malformed transaction - sees their block ignored by every honest node on the network. This is the reasoning behind the popular saying that Bitcoin is governed by nodes, not miners. The hash rate decides which valid history wins; the nodes decide what valid means.

bitnodes.io counted 25,514 publicly reachable nodes on October 9, 2026, a figure that includes 1,829 Knots nodes that no longer follow Bitcoin's main chain. Many more don't accept incoming connections, so a crawler can't reach them to count them. Luke Dashjr's counter adds an estimate for those and put the total at about 104,000 on October 10, 2026. Dashjr maintains Bitcoin Knots, and his total includes several thousand Knots nodes on versions that have left the main chain. That distributed enforcement is the real backbone of Bitcoin's security model.

See Full Node for what running one looks like in practice, and Journey: Sovereignty for why you might want to.