EndBlock

EndBlock is a concept in the Tendermint consensus engine and its application interface (ABCI) used by many blockchain ecosystems, notably those built on the Cosmos SDK. It refers to the end-of-block processing step. After all transactions in a block are executed, the application receives an EndBlock request for the corresponding block height. The EndBlock method executes module logic that should occur at block boundaries and returns an EndBlockResponse.

Typically, EndBlock logic includes updating the validator set due to stake changes, processing slashing decisions, finalizing governance outcomes, distributing or scheduling rewards, or performing maintenance tasks such as advancing unbonding queues. The EndBlockResponse may include ValidatorUpdates to alter the active validator set and a list of consensus parameter updates. It also carries events (tags) that observers can subscribe to.

EndBlock is distinct from BeginBlock, which handles per-block initialization tasks before transactions are processed. Together, they enable modular, per-block state transitions. Implementations must be deterministic and idempotent; given the same input, EndBlock should produce the same results, to preserve consensus.

In practice, EndBlock is implemented by the blockchain application. In Cosmos SDK-based chains, modules implement an EndBlocker function that receives the current block height and state, performs module-specific per-block work, and returns any validator updates or parameter changes to the consensus engine.