How Are Crypto Transactions Confirmed?

ChangeNOW.io
The Citadel
Published in
5 min readSep 10, 2021

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Knowing how your transaction is confirmed is the basis on which you can build your understanding of cryptocurrency. This is a technically difficult process, but you can grasp it without special terms — today, we will explain to you how it works. Let’s take Bitcoin as an example.

How do Bitcoin transactions get confirmed?

When you send a transaction from your wallet (where it’s signed with a private key), it gets propagated to a network of Bitcoin nodes — participants who now have to confirm it. After the primary verification, the transaction goes to a mempool (memory pool) — the place where all unconfirmed transactions are gathered and where miners (nodes) pick them to confirm.

Transactions for which users set higher fees are prioritized by miners — they are trying to make maximum profit from their work. When a node mines a block with your transaction and adds it to the blockchain, it means your transaction has been confirmed.

Why do I have to wait for confirmations?

Bitcoin block time is 10 minutes, and its block size is 1 MB — so it can’t accommodate transactions that take more space. Usually, there are more transactions that a block can take, so if you’ve set a good fee, miners will pick it in the current block, and you won’t have to wait more than 10 minutes. If the fee is low or there is a huge pile of transactions, your transaction may not fit into the first block, and you’ll have to wait 20–30 minutes until it makes it to the closest block possible.

When your transaction is added to a block, this means it has got a confirmation. When another 10 minutes pass and one more block is mined, that means your transaction now has 2 confirmations. And so on — within 24 hours, a transaction gets around 140 confirmations.

If you pay for some goods or services or deposit money on an exchange, you may be asked to wait for a few confirmations. This can be fixed (2–3 confirmations) or flexible: the more money you send in a transaction, the more confirmations it needs. For transactions worth over $10,000, 6–10 confirmations may be required, and for those worth $1 million and more, it can be about 60.

Why is that needed, given that transactions are irreversible and once they make it into a blockchain, they will stay there forever? The thing is that shops and exchanges want to protect from potential attacks on the Bitcoin network. Attacking BTC is very expensive and there haven’t been cases lately, but this is highly relevant to other coins — for instance, Ethereum Classic (ETC) has experienced two 51% attacks in the last few years.

When an attack happens, malicious actors take control over at least 51% of the network’s nodes and can put any data that they want in the blockchain. They may even cancel your transaction. However, this is possible only for the latest blocks — the older a block, the more difficult it is to reach it and alter it. 2–3 confirmations and especially 10 is a reliable indicator that nothing will happen to a transaction and it’s now forever in the blockchain.

How to set a good fee?

As we already mentioned, the higher the fee, the higher the probability that your transaction will get into the first block.

Setting this is possible in Atomic and Guarda wallets. Choose the currency, click “Send”, and then “Set fee”. You will see that fees are measured in sat/B, or satoshis per byte (1 Satoshi is one hundred millionth of Bitcoin — 0.00000001 BTC). By default, the fee will be set for the fastest confirmation time (about 100 sat/B).

Here, you can see how fast the transactions with different fees are confirmed. If you are not in a hurry, set a lower fee to save money — but make sure you don’t make it too low. With fees below 5–10 sat/B, a transaction may get stuck for hours and even days: miners will be disincentivized to take it from the mempool. To check the overall state of the latter, see Mempool.Space.

How long do I have to wait for a confirmation?

Bitcoin is one of the slowest networks — its block time is 10 minutes. See how the probability of a block being mined depends on time:

Ethereum was one of the first platforms to drastically improve this indicator, and its block time is 15 seconds. Even this is considered quite long today: such coins as Solana and Nano process transactions in less than a second, and the fees are extremely low or even absent.

Can ChangeNOW speed up the confirmation time for my transaction?

Unfortunately not, even though we would love to. We can only recommend you to set the fees higher if you want your transaction processed faster by miners.

My transactions get stuck often. What can I do?

Maybe you’re using a poorly working wallet. Try using Atomic Wallet, Trust Wallet, or Guarda Wallet. They sync well with the blockchain, and their support team resolves the issues promptly.

How do I check if my transaction was confirmed?

When you send crypto from your wallet, it shows you the transaction hash — a unique transaction identifier. Paste it into the Bitcoin or Ethereum block explorer’s search bar to see if the transaction was confirmed and if it was, how many times. For other coins, find their block explorers on the internet and repeat the steps.

I used ChangeNOW to swap my coins, and my transaction got stuck. What can I do?

Contact our support team and describe as many details as you can. We will get back to you promptly.

Tips to spend less on network fees

  • Don’t send the coins when the blockchain is congested — you can see this data in the mempool. Usually this happens when the coin’s price grows or drops rapidly, following with a surge in transaction fees. If you don’t need to send money urgently, wait for a day or two.
  • If several hours won’t make much difference to you, lower the fee. Don’t make it too low, though — otherwise your transaction may get stuck.
  • If you are planning a few similar transactions, think of organizing them into one single payment. Fees don’t depend on the transaction size, so by putting a few into one, you’re saving a considerable amount of money.

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ChangeNOW.io
The Citadel

ChangeNOW is an instant cryptocurrency exchange service for limitless crypto conversions. We support over 850 coins and are account-free! https://changenow.io/