What Is a Transaction Confirmation?
A transaction confirmation shows that a crypto transfer has been included in a block, and how many blocks have been added on top since. The more confirmations, the harder the transaction is to reverse.
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A transaction confirmation tells you that a crypto transfer has been included in a block on the blockchain, and the confirmation count tells you how many blocks have been added on top of it since. Your transaction gets its first confirmation when it lands in a block, and each new block adds one more. The higher the count, the harder the transaction is to reverse, which is why exchanges wait for a set number before crediting deposits.
How are confirmations counted?
A transaction that has been broadcast but not yet included in a block waits in the mempool with zero confirmations. If your transaction was included in block 900,000 and the latest block is 900,005, it has six confirmations. Block explorers do this math for you and display the count on the transaction page.
How many confirmations are enough?
On Bitcoin, the long-standing rule of thumb is that six confirmations make a transaction effectively final. The convention grew out of the probability analysis in Satoshi Nakamoto’s whitepaper and years of industry practice. Nothing in the protocol declares a transaction irreversible after six blocks; each additional block simply raises the cost for an attacker trying to rewrite history.
The number you need depends on the amount and the network:
- Small payments: some merchants accept one confirmation, or even zero for low-value purchases.
- Exchange deposits: each exchange sets its own threshold for each network, and a few confirmations is common for Bitcoin. The current figure is shown on the deposit screen.
- Proof-of-stake chains: on Ethereum, finality matters more than a raw count; blocks normally finalize in about 13 minutes.
The same number of confirmations does not mean the same security everywhere. Six Bitcoin confirmations and six blocks on a chain with second-long block times represent very different amounts of time and attack cost.
Layer 2 networks add another wrinkle. The “confirmed” status you see within seconds is a soft commitment from the operator that orders transactions. Posting that data to Ethereum and having it finalize there happens later, which is why withdrawing back to mainnet can take longer.
Why are confirmations slow?
Two things set the pace: how long your transaction waits to get into its first block, and how quickly new blocks follow. The first depends mostly on the fee you paid. On a busy network, low-fee transactions can wait several blocks or even hours. After that, Bitcoin’s average ten-minute block time takes over, but blocks don’t arrive on a fixed schedule, so three confirmations won’t necessarily take exactly 30 minutes.
If bitcoin you sent to an exchange shows as confirmed on an explorer but hasn’t reached your balance, the exchange probably hasn’t hit its confirmation threshold yet. Sending a second transfer won’t help. You can follow progress with the TXID.
What doesn’t a confirmation guarantee?
A confirmation only proves the transaction was recorded on-chain. A transfer to the wrong address confirms just as well, and it can’t be undone. A deposit sent over a network the exchange doesn’t support will also look successful on-chain but may never be credited. That’s why checking the network, address and any memo before you hit send matters; see our guide on choosing the right network.
Frequently asked questions
What does zero confirmations mean?
The transaction has been broadcast but isn’t in a block yet. At this stage it can still be replaced or dropped, so it shouldn’t be relied on for large amounts.
How long do six Bitcoin confirmations take?
About an hour on average, though it can be shorter or longer because block intervals vary and the transaction may wait before entering its first block.