Finality describes how a blockchain treats the possibility that accepted history could later change. Networks implement finality in different ways.
What you'll understand
- In proof-of-work networks such as Bitcoin, confidence generally increases as more blocks accumulate on top of a transaction.
- Some proof-of-stake systems include checkpoint votes or related mechanisms that mark parts of the chain finalized under protocol rules.
- A reorganization occurs when nodes switch from one valid branch to another that the fork-choice rule prefers.
- Exchanges, payment systems and applications use finality assumptions when deciding when to treat an on-chain event as sufficiently settled.
Probabilistic finality
In proof-of-work networks such as Bitcoin, confidence generally increases as more blocks accumulate on top of a transaction. The probability of a deep reorganization becomes progressively lower under normal assumptions.
Applications decide how much confirmation depth they require.
Explicit finality
Some proof-of-stake systems include checkpoint votes or related mechanisms that mark parts of the chain finalized under protocol rules.
Reverting finalized history may require exceptional protocol violations or social intervention.
Reorganizations
A reorganization occurs when nodes switch from one valid branch to another that the fork-choice rule prefers. Short reorganizations can occur during normal network operation.
A reorganization is distinct from a fraudulent transaction; it is a change in which block history is canonical.
Why finality matters
Exchanges, payment systems and applications use finality assumptions when deciding when to treat an on-chain event as sufficiently settled.
The clearest way to understand this topic is to separate the protocol, the digital asset, the software interface and any third-party service. Each layer has different responsibilities, dependencies and risks.
