<p>Technically a block with just one transaction in it would be valid. However miners have an incentive to add more transactions to the block they are currently mining because they receive the transaction fees attached to those transactions.</p>

CC BY-SA 3.0
2014-05-12T15:03:31.050Z
another question... could miners ignore transactions that didn't pay fees?
a432511
CC BY-SA 3.0
2014-05-12T15:14:15.837Z
Yes; and they are actively doing that as well. Giving priority to higher fees and omitting none/lower fees.
Maran
CC BY-SA 3.0
2014-05-12T14:51:01.737Z
2014-05-12T14:51:01.737Z
Maran
<blockquote>
  <p>could miners ignore transactions that didn't pay fees?</p>
</blockquote>

<p>yes. bitcoin is voluntary system. each miner has a right to include or skip any transaction.</p>

<p>(not asked questions)</p>

<blockquote>
  <p>why do miners include free transactions?</p>
</blockquote>

<p>Why not? The system is for people, not people for system.</p>

<blockquote>
  <p>do miners include all free transactions?</p>
</blockquote>

<p>No! There are some recommended rules
<a href="https://en.bitcoin.it/wiki/Transaction_Fee" rel="nofollow">https://en.bitcoin.it/wiki/Transaction_Fee</a></p>

CC BY-SA 3.0
2014-05-12T15:20:39.380Z
2014-05-12T15:20:39.380Z
user15732
<p>I think I understand mining well enough, but what I don't get is how the blocks of transactions are assembled. According to this post - <a href="https://bitcoin.stackexchange.com/questions/148/what-exactly-is-mining">What exactly is Mining?</a> - the miners assemble the blocks and then solve for the difficulty. </p>

<p>So, once a block is solved and the miners need to create a new block, how do the miners decide how many transactions to put in the block? Could the miner just assemble a block with a single transaction? Could certain blocks contain more or less transactions than another? Thanks!</p>

<block-header><merkle-tree><mining-technical-details><transaction-selection><empty-blocks>
How Is Block Assembled?
a432511
# How Is Block Assembled?

(Asked by: username_0 on 2014-05-12)

I think I understand mining well enough, but what I don't get is how the blocks of transactions are assembled. According to this post - [What exactly is Mining?](https://bitcoin.stackexchange.com/questions/148/what-exactly-is-mining) - the miners assemble the blocks and then solve for the difficulty.

So, once a block is solved and the miners need to create a new block, how do the miners decide how many transactions to put in the block? Could the miner just assemble a block with a single transaction? Could certain blocks contain more or less transactions than another? Thanks!

**Tags:** block-header, merkle-tree, mining-technical-details, transaction-selection, empty-blocks


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## 2 answers

### Answer by username_1 on 2014-05-12. Score: 1 | Accepted answer

Technically a block with just one transaction in it would be valid. However miners have an incentive to add more transactions to the block they are currently mining because they receive the transaction fees attached to those transactions.

> **Comments:**
> **username_0**: another question... could miners ignore transactions that didn't pay fees?  
> **username_1**: Yes; and they are actively doing that as well. Giving priority to higher fees and omitting none/lower fees.  

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### Answer by username_2 on 2014-05-12. Score: 1

> could miners ignore transactions that didn't pay fees?

yes. bitcoin is voluntary system. each miner has a right to include or skip any transaction.

(not asked questions)

> why do miners include free transactions?

Why not? The system is for people, not people for system.

> do miners include all free transactions?

No! There are some recommended rules
<https://en.bitcoin.it/wiki/Transaction_Fee>


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