Blockchain finality describes the point at which a protocol treats a block or chain state as final under its own rules. The exact meaning depends on the protocol, so this article uses Ethereum as the technical example.
Ethereum’s proof-of-stake example
Ethereum’s proof-of-stake documentation describes finality through pairs of checkpoints. Validators vote on these checkpoints, and a checkpoint can become justified and then finalized when the documented voting conditions are met. The explanation includes a two-thirds staked-ETH threshold for the relevant vote.
This is a protocol process involving validator messages and state transitions. It is different from simply saying that a transaction has been seen, included in a block or waiting for additional blocks.
Why protocol scope matters
Ethereum’s proof-of-work documentation explains a different model in which confidence increases as more blocks are built on top of a transaction, rather than using Ethereum’s explicit proof-of-stake finalisation process. Other protocols may define finality differently again.
What finality does not promise
Technical finality is not a general guarantee about legal ownership, accounting treatment, a real-world event or a service provider. It means that a particular protocol has reached the state its rules describe as final.
In short
Finality is a protocol-specific technical state. Ethereum proof of stake uses checkpoint justification, validator votes and a documented threshold to finalise chain history.