A concrete example
A broadcast transaction has not yet reached inclusion or finality.
In context
Proof of work makes block production computationally expensive. Bitcoin nodes select the valid chain with the greatest accumulated work. Proof of stake instead uses committed capital, votes and protocol-defined penalties. Neither mechanism allows a producer to override every validity rule.
The related mechanism, visually
- 01Valid blocks
- 02Temporary competing branches
- 03Fork-choice rule
- 04Acceptance policy
Read these as connected concepts, not necessarily consecutive steps.
Read the explanation
Consensus coordinates participants that do not receive messages at exactly the same time. Validation asks whether a block follows the rules. Fork choice selects between eligible histories. Finality describes when reversing a result becomes sufficiently difficult or requires violating explicit protocol assumptions. These are related tasks, but no single confirmation label explains all three.
Put the mechanism into context
Two valid blocks arrive almost together. Some nodes first see block X, others Y. Sketch the temporary split and a later extension of one branch. A transaction from the discarded branch may return to pending if it remains valid. Inclusion at one instant was not a guarantee of permanent placement.
Apply it in the workshop →What this mechanism does not guarantee
Proof of work makes proposing history costly through computation; proof of stake uses bonded capital and protocol penalties. Neither lets an honest validating node accept an invalid spend merely because many producers support it. Safety concerns conflicting accepted results; liveness concerns continued progress. A network disruption may harm progress without immediately creating conflicting finalized histories.
Explore the full explanation
Consensus and finality
Validation asks whether an operation follows the rules.