user86664: why sometimes block has 16 transactions and sometimes over 2000?
I checked it on https://blockexplorer.com/blocks.
Thank you

user60443: Since the block size is fixed (but has changed since genesis block) there are 2 main reasons:

Transactions are not all the same size in bytes. One transaction can have multiple inputs and outputs, increasing the size of the tx in bytes.
The market might not fill a block with transactions (esp. in the beginning blocks) because usage is low.


86664: <p>why sometimes block has 16 transactions and sometimes over 2000?
I checked it on <a href="https://blockexplorer.com/blocks" rel="nofollow noreferrer">https://blockexplorer.com/blocks</a>.
Thank you</p>
 60443: <p>Since the block size is fixed (but has changed since genesis block) there are 2 main reasons:</p>

<ol>
<li>Transactions are not all the same size in bytes. One transaction can have multiple inputs and outputs, increasing the size of the tx in bytes.</li>
<li>The market might not fill a block with transactions (esp. in the beginning blocks) because usage is low.</li>
</ol>
