A confirmation is each new block added to the blockchain after the block containing your transaction. One confirmation means your transaction is in the latest block; six confirmations (the common security threshold) means five additional blocks have been mined on top of it, making reversal computationally impractical.
What Are Bitcoin Transaction Confirmations?
2 min read
The short version
Confirmations are like layers of concrete poured over a time capsule. Each layer makes it harder to dig back down and tamper with what's buried. One layer is good; six layers means nobody short of controlling half the world's mining power could change it.
How It Works
When your transaction is first included in a block, it has 1 confirmation. Each subsequent block adds another confirmation. The security guarantee increases because reversing a transaction with N confirmations would require re-mining N blocks plus outpacing the honest chain, a task whose cost scales exponentially with N. For a 51% attacker, the probability of success drops by roughly half per confirmation. At 6 confirmations, even an attacker with 30% of network hash rate has less than a 0.1% chance of success. For very large amounts, some services wait for more confirmations.
Watching confirmations on a $50,000 transaction
You receive 0.83 BTC ($50,000) from an exchange. At 0 confirmations (mempool only), the transaction is visible but theoretically reversible. At 1 confirmation (~10 min), a miner has included it in a block, basic security. At 3 confirmations (~30 min), most wallets show it as "confirmed." At 6 confirmations (~60 min), the exchange considers it fully settled. A merchant selling a $10 coffee might accept 1 confirmation; a car dealership accepting $50,000 should wait for 6.
What People Get Wrong
Unconfirmed transactions are dangerous
For small amounts, unconfirmed transactions are usually safe. Double-spend attacks require specific technical conditions and are rare. Most wallets display them as pending, not failed.
Six confirmations is a hard rule
It is a convention, not a protocol rule. The appropriate number depends on the transaction amount and your risk tolerance. Some services accept 1-2 for small payments.
More confirmations means faster
More confirmations just means more time has passed. Each confirmation takes ~10 minutes on average regardless of the number of prior confirmations.
Keep Reading
Sources & Further Reading
- Bitcoin Confirmation Security (Bitcoin.org)
Official guidance on confirmation requirements for different payment sizes
- Mempool.space
Track your transaction confirmations in real time
Questions People Also Ask
- How long does 1 confirmation take?
- On average 10 minutes, but it's probabilistic, it could be 2 minutes or 40 minutes. You're waiting for the next block to be mined.
- Why is my transaction stuck at 0 confirmations?
- Usually because the fee you attached is too low for current demand. The transaction sits in the mempool until a miner includes it. You can use RBF (Replace-By-Fee) to bump the fee.
- Do Lightning Network transactions need confirmations?
- Lightning payments settle instantly between channel participants. Only opening and closing channels require on-chain confirmations.