<p>A little more information is necessary to tell you exactly what happened to your transactions that were confirmed "almost instantly" but what you've said is correct:</p>

<ul>
<li>The bitcoin protocol is such that new blocks should be mined, on average, every 10 minutes. </li>
<li>A transaction is "confirmed" (has 1+ confirmation) only after being included in a block. Before this, the transaction is "pending". Some merchants require more than one confirmation for the transaction to be final, many choosing to wait for 3 confirmations before being deemed complete. </li>
</ul>

<p>However, the situation can arise where after publishing your transaction a block is then mined a few seconds later that has your transaction in it. This could give the appearance that your transaction was confirmed "almost instantly". </p>

<p>Possible source of confusion: Blocks aren't mined 10 minutes after your transaction, they're mined 10 minutes (on average) since the previous block was mined. </p>

CC BY-SA 3.0
2018-01-24T17:36:49.023Z
Thanks I understand what you say but there must be something else.. I'm pretty sure that the "almost instant effect" is not related to a block being mined seconds after.. It happened to me many times (when mempool is clear..). for example you buy a coffee, scan the qr code, click send and boom, on the merchant screen he got received.. do you know what I mean?
Rhinoted
CC BY-SA 3.0
2018-01-24T17:54:04.393Z
Yes, in that case the merchant is accepting the payment without any confirmations. The merchant's app is likely notifying the clerk that the transaction has been broadcasted. "Received" does not mean confirmed in this case. He is trusting that the customer would not go through the hassle of a double-spend to steal a coffee.

His other option is to wait for one confirmation before giving you the coffee, which could take a while, and would lead to unhappy customers!
Matt Popovich
CC BY-SA 3.0
2018-01-24T17:58:52.357Z
so the transaction is not even in a block yet right?
Rhinoted
CC BY-SA 3.0
2018-01-24T18:07:42.833Z
Probably not. The transaction would be sitting in the mempool along with all other pending transactions waiting to be included in a block and confirmed.
Matt Popovich
CC BY-SA 3.0
2018-01-24T18:49:10.000Z
Sure! If you feel this answer has helped, feel free to vote or accept it. See: [What should I do when someone answers my question?](https://stackoverflow.com/help/someone-answers)
Matt Popovich
CC BY-SA 3.0
2018-01-24T17:24:49.503Z
2018-01-24T17:33:00.977Z
2018-01-24T17:33:00.977Z
Matt Popovich
<p>I have a basic question on Bitcoin and blockchain:</p>

<p>Sometimes transactions are confirmed almost instantly, but there should be a new block every 10 minutes, so how is it possible? A transaction can be confirmed only after being included in a block, right?</p>

<p>thanks!</p>

<confirmations><block-interval>
Why are Bitcoin transactions sometimes confirmed instantly if blocks are mined every 10 minutes?
Rhinoted
# Why are Bitcoin transactions sometimes confirmed instantly if blocks are mined every 10 minutes?

(Asked by: username_0 on 2018-01-24)

I have a basic question on Bitcoin and blockchain:

Sometimes transactions are confirmed almost instantly, but there should be a new block every 10 minutes, so how is it possible? A transaction can be confirmed only after being included in a block, right?

thanks!

**Tags:** confirmations, block-interval


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## 1 answers

### Answer by username_1 on 2018-01-24. Score: 2 | Accepted answer

A little more information is necessary to tell you exactly what happened to your transactions that were confirmed "almost instantly" but what you've said is correct:

* The bitcoin protocol is such that new blocks should be mined, on average, every 10 minutes.
* A transaction is "confirmed" (has 1+ confirmation) only after being included in a block. Before this, the transaction is "pending". Some merchants require more than one confirmation for the transaction to be final, many choosing to wait for 3 confirmations before being deemed complete.

However, the situation can arise where after publishing your transaction a block is then mined a few seconds later that has your transaction in it. This could give the appearance that your transaction was confirmed "almost instantly".

Possible source of confusion: Blocks aren't mined 10 minutes after your transaction, they're mined 10 minutes (on average) since the previous block was mined.

> **Comments:**
> **username_0**: Thanks I understand what you say but there must be something else.. I'm pretty sure that the "almost instant effect" is not related to a block being mined seconds after.. It happened to me many times (when mempool is clear..). for example you buy a coffee, scan the qr code, click send and boom, on the merchant screen he got received.. do you know what I mean?  
> **username_1**: Yes, in that case the merchant is accepting the payment without any confirmations. The merchant's app is likely notifying the clerk that the transaction has been broadcasted. "Received" does not mean confirmed in this case. He is trusting that the customer would not go through the hassle of a double-spend to steal a coffee.  His other option is to wait for one confirmation before giving you the coffee, which could take a while, and would lead to unhappy customers!  
> **username_0**: so the transaction is not even in a block yet right?  
> **username_1**: Probably not. The transaction would be sitting in the mempool along with all other pending transactions waiting to be included in a block and confirmed.  
> **username_1**: Sure! If you feel this answer has helped, feel free to vote or accept it. See: [What should I do when someone answers my question?](https://stackoverflow.com/help/someone-answers)  

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