What is Finality?
Finality refers to the guarantee that a transaction or block cannot be reversed once it has been completed.
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What Does Finality Mean?
Finality describes the conditions under which a blockchain transaction is accepted as no longer reversible. In Turkish, it is referred to as “kesinleşme.” The initial appearance of a transaction in a block and its finalization may not be the same stage. While the network chooses between short-term competing histories, some blocks may fall outside the valid chain.
In Bitcoin, finality is treated probabilistically. As new blocks are added after the block containing the transaction, altering the history becomes increasingly difficult. There is no fixed number of confirmations where the protocol dictates that it will never change under any circumstances from that point forward. Users and platforms determine the number of confirmations they wait for based on their specific risk tolerance.
The Difference in Ethereum
In Ethereum’s Proof of Stake mechanism, specific checkpoints are finalized through validator votes. Reversing a finalized history is distinct from a short chain reorganization (reorg) during normal operation; it requires severe conditions, such as massive economic penalties and the breakdown of the protocol’s security assumptions. If there is insufficient validator participation, finalization may be delayed even if blocks continue to be produced.
Appearing Fast Is Not the Same as Finality
An application displaying “completed” in just a few seconds may not mean that all security stages of the underlying network have finished. Especially in Layer 2 networks, the rapid acceptance provided by a sequencer and the subsequent submission and finalization of that data on the mainnet are separate steps. Withdrawal times from a bridge can also be significantly affected by these stages.
For example, you might see your token balance updated immediately on one network but have to wait longer to withdraw it to another. These two screens are not necessarily in conflict; they simply represent different stages of completion. When comparing transaction speeds, it is important to distinguish whether you are measuring the initial appearance time, finalization, or the time the platform takes to credit the balance.