What Is ‘Finality’ in a Blockchain Context?

Finality refers to the guarantee that once a transaction is recorded on the blockchain, it cannot be changed, reversed, or canceled. In Proof-of-Work systems, finality is probabilistic; the longer a transaction has been buried under subsequent blocks, the more final it is considered.

In some Proof-of-Stake systems, finality can be deterministic, meaning it is guaranteed after a certain number of network approvals. It is a key measure of a blockchain's security and immutability.