Node (Full vs. Light vs. Archive)

A node is simply a computer that participates in a blockchain network by running the blockchain’s software. Nodes store copies of the blockchain data, communicate with other nodes to share new transactions and blocks, and enforce the rules of the protocol. Together, all the nodes form the decentralized infrastructure that makes the blockchain function — there is no central server.

A full node downloads and independently verifies every block and every transaction since the genesis block, requiring significant storage space but providing complete independence from third parties. A light node downloads only the block headers — small summaries — and requests specific data from full nodes as needed, making them practical for smartphones and devices with limited storage. An archive node stores not just the current state of the blockchain but every historical state at every block height — essential for researchers, blockchain explorers, and applications that need to query what the state of any wallet was at any point in the past, but requires enormous storage space (often tens of terabytes for a chain like Ethereum).

Example: Think of three kinds of library patrons. The full node is someone who has read and personally verified every book in the library and keeps their own complete copy. The light node only keeps the catalog and calls the library whenever they want to read something specific. The archive node is the head librarian who not only has every book, but also keeps every previous edition and every note ever made in the margins — a complete historical record going back to day one.