Block Confirmations
Confirmations · Confirmation count · Block confirmation
The number of blocks added on top of (and including) the block holding your transfer; an exchange credits a deposit once its required number is reached.
Simple explanation
Background: Korean investors shorten the word to 컨펌 ("confirm") and ask how many 컨펌 a deposit needs. Every coin moved between Korean and overseas exchanges waits for confirmations, which is a big part of why a transfer takes minutes rather than seconds.
When you send a coin, the transfer first waits in the network's queue and is then put into a new block. The moment it lands in a block is one confirmation, and every new block after that adds one more. "Six confirmations" means five more blocks have been stacked on top of the one holding your transfer.
Why wait? Now and then a blockchain swaps its most recent few blocks for different ones (a reorganization). A freshly included transfer can then drop out of the record, and an attacker can use that gap to spend the same coins twice (a double spend). The more blocks pile up on top, the harder the record is to overturn, so an exchange credits a deposit only after its required number of confirmations. The guide site bitcoin.org advises waiting for at least six confirmations on high-value bitcoin transfers.
The wait is roughly the confirmations required times the time between blocks. Bitcoin produces a block about every 10 minutes on average, but that is not fixed: a block can come much sooner or much later, and a low transaction fee can mean a longer wait to get into the first block. Ethereum has a block slot every 12 seconds, and after a while blocks reach "finality", after which they cannot be reversed. On chains that produce a block every few seconds, even a long confirmation count can take only a short time.
How many confirmations are required differs by exchange and coin. Two exchanges can ask for different numbers on the same bitcoin deposit, and exchanges change them when conditions change. On small chains, rewriting blocks is not just theory: after a series of so-called 51% attacks on Ethereum Classic (ETC) in 2020, some exchanges sharply lengthened the confirmation time for its deposits or halted deposits and withdrawals. Check the receiving exchange's deposit guide for the actual figure.
A deposit is not always credited the moment the count is reached. Exchanges may still run Travel Rule checks or their own reviews, and a withdrawal goes through the exchange's own processing, such as a withdrawal review, before it is even broadcast to the blockchain. Exchanges keep most customer coins offline in cold wallets, so when withdrawals pile up, moving coins into the hot wallet that sends them can slow things down. If a transfer sits at "processing" for a long time, first work out whether it has reached the blockchain yet or is waiting for confirmations.
Your exchange's deposit and withdrawal history shows a TXID (transaction ID) for each transfer. Paste it into that coin's block explorer to see whether it is in a block and how many confirmations it has. Do not send the same coins again because a transfer looks slow; you could end up sending twice. During network outages or upgrades, exchanges often suspend the coin's deposits and withdrawals altogether.
It ties straight into the kimchi premium. Prices keep moving at home and abroad while a coin waits for confirmations, so the premium you saw when you sent it may have shrunk or vanished by the time it arrives. Moving a coin or network with fast blocks and few required confirmations shortens the wait, but the exchanges' own processing time still applies.
CoinGaja's Kimchi Premium Calculator takes fees and order-book slippage out of the premium, but it does not count the time spent waiting for confirmations or price moves during that time. The Deposit and withdrawal suspensions page shows each coin's deposit and withdrawal status, read from the exchanges' official APIs every 5 minutes.
Example
A bitcoin block comes about every 10 minutes on average (it can be faster or slower)
If the receiving exchange requires 3 confirmations → 3 × 10 minutes = about 30 minutes on average before the deposit is credited
You buy ₩10,000,000 (about $7,140) of a coin abroad and send it at a kimchi premium of +3.00% → expected gain ₩10,000,000 × 3% = ₩300,000 (about $214)
If the premium shrinks to +1.00% during those 30 minutes → ₩100,000 (about $71); if it turns to -0.50% (a reverse premium) → -₩50,000 (about -$36) (assuming the overseas price stays put)
On Ethereum, with a block every 12 seconds, waiting for 30 confirmations → 30 × 12 seconds = 6 minutes
Fees are left out
※ Example numbers, for illustration only
See it on CoinGaja
Related terms
Comments · ask anything about this term
Comments
No comments yet.