Blockchain consensus is the set of protocol rules and processes a network uses to agree on a valid history or state. It is a technical term, not a promise that every participant agrees about everything outside the network.
Why a network needs consensus
Blockchain networks have multiple independent computers receiving and checking information. Consensus mechanisms provide the rules for deciding which proposed blocks or state changes count within that system.
Bitcoin’s white paper describes a peer-to-peer system in which nodes work with a chain of timestamped blocks and accept the longest proof-of-work chain as evidence of the sequence of events they have seen. Ethereum documentation describes proof of stake as its consensus mechanism.
Consensus is network-specific
There is no single consensus arrangement used by every blockchain. Proof of work and proof of stake are two different approaches. The data checked, the participants’ roles and the conditions for accepting a block can differ from one network to another.
What consensus does not mean
Consensus does not prove that data originating outside the network is correct. It does not identify participants, guarantee the legal meaning of a record, or settle real-world disagreements. It concerns the operation of a defined technical system.
Sources
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