A full node is a critical component of a blockchain network, responsible for maintaining its security, transparency, and decentralization. Its primary functions include:

Transaction Validation – A full node independently verifies every transaction against the network’s consensus rules (e.g., checking digital signatures, preventing double-spending).

Block Validation – It validates new blocks, ensuring they follow protocol rules (e.g., correct proof-of-work/proof-of-stake, valid transactions).

Storing the Blockchain – Unlike lightweight nodes, a full node downloads and stores the entire blockchain history, preserving network integrity.

Relaying Data – Full nodes propagate valid transactions and blocks to other nodes, helping synchronize the network.

Enforcing Consensus Rules – By rejecting invalid blocks, full nodes prevent malicious actors from altering the blockchain (e.g., enforcing Bitcoin’s 21M supply cap).

Privacy & Self-Sufficiency – Users running full nodes don’t rely on third parties to verify transactions, enhancing security and reducing trust risks.

Full nodes also support decentralization, the more nodes there are, the harder it is for any entity to control the network. While they don’t earn rewards like miners or stakers, their role is vital for censorship resistance and trustless operation. In proof-of-work (PoW) systems like Bitcoin, full nodes enforce miners’ compliance with rules; in proof-of-stake (PoS) networks like Ethereum, they validate stakers’ actions. Running a full node requires significant storage and bandwidth, but is the gold standard for participating in a blockchain’s governance.