Block

Overview

Blocks organize blockchain history into discrete units. A block normally contains or commits to a set of transactions, identifies its parent, and includes metadata needed for validation and consensus. The exact fields differ by protocol.

In Bitcoin, the block header commits to the previous block and the Merkle root of the block’s transactions. Miners search for a header hash that satisfies the proof-of-work target. In Ethereum proof of stake, a validator proposes a beacon block that includes consensus information and an execution payload containing transactions and state-related commitments.

Nodes validate a proposed block before accepting it. They check its structure, parent relationship, transaction validity, resource limits, signatures or proof, and resulting state transition. A valid block can still be replaced if the network later selects a competing chain, unless it has reached the protocol’s finality threshold.

Blocks are not merely folders of transactions. They are consensus objects that let independent nodes agree on transaction order and the progression of state.

Blocks create an ordered history that participants can reproduce. A node checks the block’s parent reference, consensus proof or signatures, transaction validity, resource limits, and resulting state commitments before accepting it. Invalid content cannot become valid simply because a producer included it.

The relationship between a block and final settlement varies by protocol. In proof-of-work systems, confidence usually increases as later blocks build on top of it. In proof-of-stake systems, validator votes and checkpoints may provide explicit finality. Some blocks can be valid when first observed but later become stale or orphaned because the network chooses a competing branch. Applications should therefore distinguish block inclusion from confirmation and finality when deciding whether a payment is settled.