Key takeaways
- A transaction is unconfirmed until a miner includes it in a block. That block gives it its first confirmation.
- Each further block built on top adds one confirmation and makes reversal harder.
- Blocks are targeted at roughly ten minutes apart, but actual gaps vary, so waiting times vary too.
- The fee rate you attach affects how soon miners pick your transaction up.
- How many confirmations to wait for is a choice made by the recipient, not a fixed rule.
For information only. Not investment advice. This guide explains how the network works and makes no prediction about price. Don't invest unless you're prepared to lose all the money you invest.
The short answer
When you send Bitcoin, the transaction is broadcast to the network and waits among other pending transactions. It is confirmed when a miner includes it in a block that the rest of the network accepts. That block is its first confirmation, and every block added afterwards adds another. More confirmations mean the transaction is harder to reverse.
This guide builds on What is Bitcoin and how does it work?, which explains the ledger, keys and mining in more general terms.
Step one: the transaction is broadcast
Your wallet builds a transaction that names the coins you are spending and the address that will receive them, then signs it with your private key. It sends the signed transaction to a few nodes, which check it against the rules and pass it on. Nodes reject a transaction that, for example, spends coins already spent or carries an invalid signature.
At this point the transaction has been seen by the network but is not part of the ledger. Wallets usually show it as pending or unconfirmed, and the recipient may see it arriving but should not treat it as settled.
Step two: waiting in the mempool
Each node keeps its own list of valid transactions that are waiting to be mined, usually called the mempool. There is no single shared queue, so different nodes can hold slightly different lists. Miners draw from their own view of waiting transactions when they assemble a block.
Space in each block is limited, so miners cannot include everything at once. Because they collect the fees from the transactions they include, they generally favour transactions that pay more for the space they take up. A transaction paying a low fee rate when many others are waiting may sit for a long time.
Step three: a miner includes it in a block
Miners assemble a candidate block from waiting transactions and compete to find one that meets the network's difficulty target, a process called proof of work. When a miner finds a valid block it broadcasts it, and nodes check it before accepting it. Your transaction now has one confirmation.
The protocol adjusts difficulty so that blocks arrive on average about every ten minutes. That is an average. Blocks are found at random, so one may follow the last within moments and another may take considerably longer than ten minutes. Nobody can promise the time of the next block.
What the number of confirmations means
The confirmation count is the number of blocks from the one containing your transaction up to the latest block, inclusive. Each new block is built on top of the previous one, so to undo your transaction someone would have to produce a competing chain that excludes it and have the network adopt that chain over the one it already follows. The Bitcoin white paper calculates that the chance of an attacker catching up falls rapidly as blocks are added.
| Confirmations | What it means |
|---|---|
| 0 | Seen by the network but not in a block. It can still be dropped or replaced. |
| 1 | In the latest block. Reversal is possible only if the network switches to a competing chain, which is uncommon. |
| 2 or more | Further blocks have been built on top. Each makes a reversal progressively less likely. |
The protocol sets no universal threshold. Exchanges, merchants and wallets decide how many confirmations they need before treating a payment as final, and they often ask for more on larger amounts. Check the policy of the party receiving your payment rather than assuming a number.
Fees and why transactions can be slow
A Bitcoin transaction fee is the difference between the coins going in and the coins coming out. It is not a percentage of the amount sent. Miners are paid according to how much block space a transaction occupies, so a transaction with many inputs can cost more than a simple one for the same amount.
When few transactions are waiting, a low fee rate may be picked up promptly. When many are waiting, a low fee rate can mean a long delay. Many wallets estimate a suitable fee rate for a chosen speed, and some let you raise the fee on a waiting transaction if the wallet supports it. Network fees are separate from what an exchange charges; the CoinCorner fees page lists its own published charges.
What can go wrong
- Stuck transactions. A low-fee transaction can wait a long time. If nodes drop it, the coins return to being spendable from the sender's point of view, but this is not instant or guaranteed on any schedule.
- Competing blocks. Occasionally two miners find a block at nearly the same time. The network follows one, and transactions in the other return to waiting. This is why one confirmation is weaker than several.
- Wrong address. Once confirmed, a payment to the wrong address cannot normally be undone. Check the address before you send.
- Scams that exploit speed. Anyone urging you to send Bitcoin urgently, or to release a payment before it confirms, should be treated with caution; the FCA publishes guidance on crypto investment scams.
Faster payments: Lightning
Waiting for blocks is a poor fit for small everyday payments. The Lightning Network moves payments between channels that are opened and closed with on-chain transactions, so individual payments do not each wait for a block. The Lightning Network guide explains channels and routing.
Receiving, holding and withdrawing
If you buy Bitcoin through an exchange, your balance is normally shown as soon as the purchase completes, and the confirmation count matters when you move Bitcoin on or off the platform. A deposit from another wallet generally needs the exchange's required confirmations before it is credited. How CoinCorner holds customer Bitcoin, including the multi-signature Vault, is covered on the security page. Common account and withdrawal questions are answered in the FAQ, and the buying guide covers the purchase process. CoinCorner Ltd is registered with the Isle of Man Financial Services Authority as a designated business for anti-money-laundering oversight only. That is not a licence, and CoinCorner is not regulated by the FCA.
Frequently asked questions
What is a Bitcoin confirmation?
A confirmation is a block that contains your transaction, counted together with every block added on top of it. One confirmation means the transaction is in the latest block; two means one more block has been built after it, and so on. Each one makes the transaction harder to reverse.
How many confirmations are enough?
The protocol sets no single number. Recipients choose their own threshold, and larger amounts usually justify waiting for more blocks. Six is a commonly quoted convention, but it is a custom rather than a rule written into Bitcoin. Check the policy of whoever is receiving the payment.
Why is my transaction still unconfirmed?
Most often the fee rate you attached is low compared with other waiting transactions, so miners are choosing others first. Blocks are also found at irregular intervals, so even a well-paid transaction can wait longer than ten minutes.
Can an unconfirmed transaction be cancelled?
Not directly. Nodes may eventually drop a transaction that stays unconfirmed for long enough, after which the coins can be spent again, but that is up to each node. Some wallets can replace a waiting transaction with a higher-fee version if it was flagged to allow this.
Can a confirmed transaction be reversed?
Not by anyone with a button. Undoing a transaction would mean the network adopting a different chain of blocks, which becomes less likely with each confirmation. Reorganisations of the most recent block or two can happen as part of normal operation, which is why recipients wait.
Do Lightning payments need confirmations?
Not for each payment. Lightning payments move between channels that were opened with an on-chain transaction, and that opening and closing transaction is confirmed in the usual way.
Sources
The statements about how the protocol works come from the documents below, which are given so that you can check each point against the original. This guide was written on 15 October 2026. Where a figure such as a confirmation threshold is a convention rather than a protocol rule, the text says so.
- Satoshi Nakamoto, Bitcoin: A Peer-to-Peer Electronic Cash System (2008): https://bitcoin.org/bitcoin.pdf
- Bitcoin Project, Developer Guides (transactions, block chain, mining): https://developer.bitcoin.org/devguide/
- Financial Conduct Authority, Crypto investment scams: https://www.fca.org.uk/consumers/crypto-investment-scams