What Is Finality?
Finality is the moment you can stop refreshing. A transaction is broadcast, then included in a block, then buried under more blocks until reversing it is either absurdly expensive or, on some designs, protocol-forbidden. "Confirmed" in a wallet is a setting, not a law of nature. Different chains mean different waits.
How It Actually Works
- Bitcoin is probabilistic. Six confirmations became convention because a rewrite that deep requires outrunning the honest miners. It is never literally impossible, only economically ridiculous at current hash rate. Exchanges pick their own depth.
- Ethereum after the Merge aims at economic finality. Checkpoints get justified and finalized by validators. Reversing a finalized block means burning a huge slice of staked ETH. That is a different kind of expensive.
- Fast chains advertise fast finality and sometimes mean "a leader said so." Read whether finality is cryptographic, economic, or social. Solana and various L2s have their own clocks and their own caveats, including training-wheel upgrade keys.
Risks and Common Mistakes
- Treating one confirmation as payment received, especially on a chain that reorgs under load. Wait for the venue's stated depth before shipping goods or unlocking an account.
- Assuming L2 "instant" equals L1 settled. Optimistic rollups still have a challenge window if you withdraw the native way; see bridges.
- Reorg scams and zero-conf acceptance on small coins where hash rate is cheap to rent.
When It Matters
Accepting payment, bridging, and deciding when a trade is actually done. The explorer skill in my Etherscan review is how you check inclusion yourself instead of trusting a spinner.
Related Terms
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