Overview
Probabilistic finality is the increasing confidence that a transaction will not be reverted as more blocks are added on top of it. It is the finality model of proof-of-work chains like Bitcoin. Finality is never absolute but grows stronger over time.
How It Works
Each new block requires an attacker to redo more work to rewrite history, so the cost of reversal grows exponentially with depth. After enough confirmations, reversal becomes economically impractical. Users choose how many confirmations to wait based on the amount at risk.
Why It Matters
Probabilistic finality balances security and speed: it lets chains operate without a fixed checkpoint but requires users to wait for confidence. Understanding confirmation depth is essential for payments and exchange deposits.
Related Concepts
Probabilistic Finality contrasts with the economic finality of proof-of-stake. It depends on the Longest Chain Rule and Proof of Work security.