Event Log

Indexed records emitted by smart contracts when defined events occur (a transfer, an approval, a swap). Events are written to a special structure in each transaction's receipt and are visible to off-chain observers but not readable by other contracts. Event topics (the indexed fields) are searchable on block explorers; non-indexed fields appear in the data section. Most on-chain analytics — Dune queries, The Graph subgraphs, Etherscan's token-transfer pages — reconstruct activity by parsing event logs rather than re-executing transactions.