// GLOSSARY -- BLOCKCHAIN & CRYPTO FUNDAMENTALS

What is Finality?

1 min read Updated

Finality is the guarantee that a blockchain transaction cannot be reversed, altered, or removed once confirmed — the point at which a transaction is considered permanently settled.

WHY IT MATTERS

Finality answers the question: 'When is my transaction truly done?' Different chains provide different finality guarantees. Bitcoin's finality is probabilistic — each new block makes reversal exponentially harder, but there's always a theoretical possibility. Ethereum provides economic finality after ~15 minutes.

For applications, finality determines when you can trust a payment. Exchanges wait for multiple confirmations before crediting deposits. DeFi protocols treat transactions as final after block inclusion. The appropriate finality requirement depends on the transaction value and risk tolerance.

Instant finality (achievable on some PoS chains) is critical for payment applications where users expect immediate confirmation.

FREQUENTLY ASKED QUESTIONS

How long until finality?
Bitcoin: ~60 minutes (6 confirmations). Ethereum: ~15 minutes (2 epochs). Solana: ~13 seconds. Some PoS chains achieve instant finality. L2s inherit L1 finality for security.
What is economic finality?
The point where reversing a transaction would cost more than the value at stake. On PoS Ethereum, finalizing an epoch means at least 1/3 of staked ETH would be slashed to revert.
Can finalized transactions be reversed?
Technically, a consensus failure or 51% attack could revert 'final' transactions. In practice, the economic cost makes this essentially impossible on major chains.

FURTHER READING

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