A node is a foundational structural unit of a blockchain network. It is any computer or server connected to the decentralized peer-to-peer network running specific software to store, transmit, and validate transactional data.
Key Roles of a Blockchain Node
- Data Storage: Nodes maintain a copy of the distributed ledger, ensuring the blockchain's history remains verifiable and permanent.
- Transaction Validation: They check incoming transactions against established network protocol rules before broadcasting them to adjacent peers.
- Consensus Participation: In consensus systems like Proof of Work (PoW) or Proof of Stake (PoS), specialized nodes propose, verify, and finalize new blocks.
Common Types of Nodes
- Full Nodes: Store the complete blockchain history and independently verify every transaction and block to maintain network security.
- Lightweight (Light) Nodes: Store only essential block header data to minimize memory usage, depending on full nodes to process transactions.
- Archive Nodes: Retain the complete state history of every block, permitting deep querying of historical smart contract states.
- Validator/Mining Nodes: Actively generate new blocks and secure the network in exchange for block rewards and transaction fees.
By distributing responsibilities across thousands of independent nodes worldwide, blockchain networks eliminate single points of failure and preserve decentralization.