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What is a consensus mechanism?
A consensus mechanism is the set of rules and incentives that lets a network of independent computers agree on one version of a blockchain without a central authority. The two main kinds are proof of work and proof of stake.
What it means for you
The mechanism decides what an attacker would need to rewrite recent history: most of the computing power under proof of work, or a large amount of staked coins under proof of stake. It also sets how long you wait before a payment counts as final.
How it works
A consensus mechanism does two jobs. Sybil resistance makes influence cost something real, so an attacker cannot win by running many fake nodes: computing power and energy under proof of work, staked coins under proof of stake. A fork-choice rule tells every node which chain to follow when valid blocks compete: Bitcoin nodes follow the chain with the most accumulated work, while Ethereum weighs chains by validator votes scaled by stake, and finalizes checkpoints once validators holding two-thirds of staked ETH vote for them.
Sources: ethereum.org: Consensus mechanisms, Bitcoin developer guide: Block chain, ethereum.org: Proof-of-stake · checked 4 October 2026
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