Full Node

A full node is a blockchain node that downloads and independently verifies every block and transaction against the network's consensus rules, rather than trusting anyone else's copy of the ledger. It checks signatures, ensures no coins are created out of thin air, and rejects invalid blocks even if a majority of miners or validators produced them. This makes full nodes the ultimate arbiters of what the rules of a blockchain actually are.

Running a full node requires meaningful resources: the software must first sync the entire chain history, which for Bitcoin means processing hundreds of gigabytes of data, and for some high-throughput chains far more. For example, a user running Bitcoin Core on a home computer can point their own wallet at it and confirm that a payment they received is genuine, without relying on a block explorer website or an exchange's word.

A common misconception is that full nodes mine or earn rewards; they do not — they validate and relay, while block production is a separate role. Full nodes matter for decentralization because they are the check on everyone else's power: if miners or a foundation tried to change the rules, blocks breaking those rules would simply be ignored by the network's full nodes. The easier it is for ordinary people to run one, the harder the network is to capture, which is why chains face a constant design tension between higher throughput and keeping full-node requirements affordable.