Archive Node

An archive node stores the full historical state of a blockchain — the balance and contract storage of every account at every past block — rather than only the current state plus the blocks needed to verify it. That makes it far larger and more expensive to run than an ordinary full node, and it is what any service needs in order to answer questions about the past: what an address held at a given block, or how a contract's storage looked immediately before an exploit. Block explorers, analytics platforms and tax tools depend on archive nodes, either their own or a provider's.