What Is the Difference between “Justified” and “Finalized” Blocks?
A block is considered "justified" when two-thirds of the validators have attested to it, indicating strong agreement. A block becomes "finalized" when the subsequent block is also justified.
Finalization requires two consecutive epochs (a period of 6.4 minutes) of two-thirds supermajority attestations. Finalized blocks are considered irreversible, meaning they cannot be reverted without a massive, coordinated, and economically suicidal attack.
Glossar
Finality Mechanism
Assurance ⎊ Finality Mechanism refers to the consensus protocol feature that guarantees, with an extremely high degree of probability or certainty, that a recorded transaction or state change on the blockchain cannot be reversed or altered.
Finalized Blocks
Settlement ⎊ The point at which a block of transactions is permanently added to the blockchain ensures that the data cannot be altered.
Two Consecutive Epochs
Periodicity ⎊ Two Consecutive Epochs defines the specific, sequential time interval required in certain Proof-of-Stake consensus mechanisms for a block to transition from a justified state to a finalized, irreversible state.