Log topic

A log topic is one of up to four indexed 32-byte values attached to an event log, where topic0 is the keccak hash of the event signature and the rest are indexed arguments.

Topics make logs searchable. Topic0 identifies which event fired (the keccak256 of its signature, like Transfer(address,address,uint256)), and subsequent topics hold indexed arguments such as sender and recipient addresses. Because topics are indexed, eth_getLogs can filter a huge history down to matching events by topic and address without scanning full transaction data. Our decoded-log responses map these topics back to named parameters, so you filter by topic on the archive RPC and read human-readable fields in return.