How many confirmations does bitcoin need, and why a swap waits for them

What is a bitcoin confirmation

A transfer that has just been sent sits in the mempool, the shared queue of unconfirmed transactions. A miner picks it up from there and includes it in a block. From that moment the transaction has one confirmation.

After that the count grows by itself. Every new block the network puts on top of the block with your transfer adds one more confirmation. Two confirmations mean the next block already sits above yours, and six mean the transfer is buried under six blocks, its own included.

Why count blocks if the transfer is already recorded? Because the newest block is occasionally replaced: two miners find a block almost at the same time, and a few minutes later the network picks one of the two branches. The deeper a transaction sits, the more it costs to rewrite. To pull a transfer out from under six blocks, someone has to redo the work of all six and outrun the rest of the network.

Why a block takes 10 minutes, and why that is only an average

Ten minutes is written into the network rules. Every 2016 blocks, roughly once every two weeks, bitcoin recalculates the mining difficulty. If blocks came faster, the puzzle gets harder, and if they came slower, it gets easier. That is how the network keeps its average pace no matter how many miners join.

But that pace is exactly an average. Finding a block works like a lottery: miners try variants, and the lucky one may turn up in a minute or in forty. Half-hour gaps between blocks happen several times a day, and nothing is broken when they do.

So "6 confirmations is an hour" is true only on average. Sometimes six blocks arrive in 35 minutes, sometimes it takes an hour and a half. Nobody knows the exact time, including your wallet, the exchange and the block explorer.

How many confirmations does bitcoin need: 0, 1, 3 or 6

The protocol has no single number. The network treats a transfer as done from the first block, and how long to wait after that is up to each recipient: an exchange, a shop or a crypto exchange without accounts sets a threshold that fits its own risks. The larger the amount, the more blocks they ask for.

Zero confirmations mean the transfer is visible but not protected by anything yet. The sender can replace it with another transaction that spends the same coins with a higher fee, and a miner will take the second one. Since Bitcoin Core 28.0, nodes accept such a replacement for any unconfirmed transaction by default, so "I already sent it, here is the hash" does not count as money.

One confirmation rules out the simplest trick. A transfer like that can be undone only if its block loses the race to a neighboring block. That is rare, and for small amounts one block is enough.

Two or three confirmations are asked for where a mistake costs real money but nobody wants to keep the customer waiting an hour. An accidental fork two blocks deep is extremely rare in bitcoin, and a deliberate one takes enormous hashing power.

Six confirmations go back to Satoshi. The bitcoin white paper calculates that an attacker with a tenth of the network's power catches up with the honest chain from six blocks behind with a probability of about 0.02%. The developer guide on bitcoin.org describes six blocks this way: the network has spent about an hour protecting the transfer, and even a lucky attacker would need a large share of the total hashing power.

Why the first bitcoin confirmation can take an hour

The first block is usually the longest wait. The rest arrive in due course, but you still have to get into the first one. There are three reasons for a delay, and they often stack up.

• The fee is below current rates. Block space is limited, miners take whoever pays more per byte, and a cheap transfer misses block after block.
• The queue grew after you sent. Your wallet priced the fee for a quiet market, and five minutes later a wave of transfers hit the mempool.
• A block simply is not found for a long time. During a forty-minute gap everyone waits, even with a generous fee.

With the third reason all you can do is wait, but the first two can be fixed. If your wallet supports RBF, the "Bump fee" button replaces the transaction with a more expensive version. That method and the second one, CPFP, are covered in detail in our breakdown of why a transaction is stuck pending. And the address format helps you pay less for the same transfer: a transaction from bc1q is lighter than one from the old addresses, and the article on bitcoin address types has a table with the weight of each.

How to check bitcoin confirmations by TXID

Every transfer has a hash, the TXID. Your wallet shows it in the transaction history, and an exchange shows it in the withdrawal details. With the hash, any block explorer, mempool.space for example, will show what is happening to the transfer. If you cannot find the hash, see the guide on where to get a TXID and how to read an explorer page.

1. Copy the TXID and paste it into the explorer's search bar.
2. Look at the status. "Unconfirmed" means the transfer is in the queue, and the number next to "Confirmations" shows how many blocks it has collected.
3. For an unconfirmed transfer, compare its fee in sat/vB with the current rates on the explorer's home page.

If there is no hash at all, the transfer has not reached the network yet. That happens with exchange withdrawals: the exchange sends withdrawals in batches, and confirmations start counting only after it broadcasts yours.

What a swap service does while it waits for confirmations

A swap starts once the incoming transfer has the required number of confirmations on its network. Before that the service can see the transaction, but the coins may still fail to arrive, so it does not send the payout. On VertEXchange this is a separate step on the exchange page: "Send" is followed by "Confirmation" with the note "Waiting for network confirmations", and only then come "Exchange" and "Done".

With bitcoin this wait is more noticeable than with other coins, and it affects which rate to choose. A fixed rate holds for about 15 minutes, and the first block may come later than that. A transfer that arrives late is not swapped at the old price: the page shows the note "The transfer arrived after the order had expired", and the money goes back to the refund address. How to pick a rate type for a slow network is covered in our article on fixed vs floating rate.

If you plan to swap bitcoin to ether to your own wallet or to any other coin, send the BTC right after creating the order and do not set the minimum fee. You can close the page in the meantime: the exchange code opens it from any device.

How long confirmations take on other networks

Bitcoin is the most unhurried of the popular networks. The others produce blocks more often, but they also count them differently: some wait for dozens of blocks, and on some the network itself declares a block final.

The speed of the incoming network decides how long you wait before the swap starts. If you want to buy Monero with bitcoin without registration, most of the time goes to BTC confirmations, and after the payout the XMR shows up in your wallet within a couple of minutes.

How to swap bitcoin to USDT without registration

No service can speed up network confirmations, so what you need from a swap service is something else: clear terms before you send and a visible status after. On VertEXchange a swap needs no account, email or phone number. You pick a pair, enter the amount and your wallet address, see the rate and the amount you will receive, and only then send the coins.

• A fixed rate holds for about 15 minutes, and a floating rate is set at the moment the transfer is received.
• The USDT goes straight to your address, and the service does not hold it.
• You can add a refund address: the coins return there if the swap does not go through.
• Personal fields of the operation are deleted 24 hours after the swap is complete.
• A support chat is on every page, and questions are resolved by exchange code.

People leaving bitcoin most often move into a stablecoin, and the handiest way is to swap bitcoin to USDT TRC20 to your own address on TRON. In the other direction there is almost no wait: when you buy bitcoin with USDT TRC20, the incoming transfer confirms in about a minute.

FAQ

How many confirmations does a bitcoin transaction need?

It depends on the recipient and the amount. One is enough for small transfers, most services wait for two or three, and six is the convention for large amounts.

How long does one bitcoin confirmation take?

About 10 minutes on average, which is the time of one block. In practice a block can arrive in a minute or in forty, and with a low fee the transfer may miss several blocks in a row.

Why has my transaction had 0 confirmations for an hour?

Most likely the fee is below current rates and miners are taking more expensive transfers. Check the transaction in an explorer by TXID and, if your wallet allows it, raise the fee with RBF.

Can I speed up a bitcoin confirmation?

You can only speed up getting into the first block: replace the transaction with a higher-fee version (RBF) or spend its output in an expensive transaction (CPFP). The following blocks come at their own pace, and the fee does not affect them.

Can a transaction be reversed after six confirmations?

In practice, no. That would take mining six blocks again and outrunning the entire rest of the network, which requires most of its hashing power.

The explorer already shows a confirmation, but my swap has not started. Why?

The service waits for its own number of confirmations, and one block may not be enough. The status is shown on the exchange page, and if the wait drags on, write to the support chat with your exchange code.