Small Block

[bitkilo]

Just noticed block 353454 only has 17 transactions in total, this seems very small to me.
https://blockchain.info/block/00000000000000000895f60353a27240389a8caf6a35c22d6cf3ff78bbf80fca

Can anyone give me a quick explanation as to why some blocks have 1000+ transactions and other much less.

[chennan]

Because at the time the block was created, the number of made transactions varies. Sometime it is high, sometimes is low. 

[shorena]

Just noticed block 353454 only has 17 transactions in total, this seems very small to me.
https://blockchain.info/block/00000000000000000895f60353a27240389a8caf6a35c22d6cf3ff78bbf80fca

Can anyone give me a quick explanation as to why some blocks have 1000+ transactions and other much less.

The time between this block and the block before[1] was 9 seconds according to bc.i. They probably did not know more transactions to put into the block. Considering the number of unconfirmed transactions at that time[2], there might be other - possibly economical - reasons.

[1] https://blockchain.info/block/000000000000000004d08b90ad76d0c6d665960ded65e3c8ef8abdf3b42a41d2
[2] ~0500 https://i.imgur.com/jzRXHYq.png

[bitkilo]

Just noticed block 353454 only has 17 transactions in total, this seems very small to me.
https://blockchain.info/block/00000000000000000895f60353a27240389a8caf6a35c22d6cf3ff78bbf80fca

Can anyone give me a quick explanation as to why some blocks have 1000+ transactions and other much less.

The time between this block and the block before[1] was 9 seconds according to bc.i. They probably did not know more transactions to put into the block. Considering the number of unconfirmed transactions at that time[2], there might be other - possibly economical - reasons.

[1] https://blockchain.info/block/000000000000000004d08b90ad76d0c6d665960ded65e3c8ef8abdf3b42a41d2
[2] ~0500 https://i.imgur.com/jzRXHYq.png

Thanks shorena, i always wanted to know why some block are much larger in size than others just never asked before.
I think i remember seeing a block once with only 1 transaction, anyone have a link to that one?

[odolvlobo]

Blocks are not required to have any transactions in them.

[minerpumpkin]

Just noticed block 353454 only has 17 transactions in total, this seems very small to me.
https://blockchain.info/block/00000000000000000895f60353a27240389a8caf6a35c22d6cf3ff78bbf80fca

Can anyone give me a quick explanation as to why some blocks have 1000+ transactions and other much less.

The time between this block and the block before[1] was 9 seconds according to bc.i. They probably did not know more transactions to put into the block. Considering the number of unconfirmed transactions at that time[2], there might be other - possibly economical - reasons.

[1] https://blockchain.info/block/000000000000000004d08b90ad76d0c6d665960ded65e3c8ef8abdf3b42a41d2
[2] ~0500 https://i.imgur.com/jzRXHYq.png

Thanks shorena, i always wanted to know why some block are much larger in size than others just never asked before.
I think i remember seeing a block once with only 1 transaction, anyone have a link to that one?

I don't have an example right now, but I think there are lists if you just look for them on the Internet. There definitely are blocks with only one transaction, sometimes a miner just gets lucky and it would be stupid of him or her not to immediately publish the block, otherwise they would risk another one submitting a block before them and thus losing the block reward.

[shorena]

Just noticed block 353454 only has 17 transactions in total, this seems very small to me.
https://blockchain.info/block/00000000000000000895f60353a27240389a8caf6a35c22d6cf3ff78bbf80fca

Can anyone give me a quick explanation as to why some blocks have 1000+ transactions and other much less.

The time between this block and the block before[1] was 9 seconds according to bc.i. They probably did not know more transactions to put into the block. Considering the number of unconfirmed transactions at that time[2], there might be other - possibly economical - reasons.

[1] https://blockchain.info/block/000000000000000004d08b90ad76d0c6d665960ded65e3c8ef8abdf3b42a41d2
[2] ~0500 https://i.imgur.com/jzRXHYq.png

Thanks shorena, i always wanted to know why some block are much larger in size than others just never asked before.
I think i remember seeing a block once with only 1 transaction, anyone have a link to that one?

You are welcome. The easiest way to find a block without many TX would be to go back to the early days. E.g. #42[1]. It still happens though, but dont know a certain block off the top of my head either.

Blocks are not required to have any transactions in them.

Isnt the coinbase TX, technically a TX? I know miners dont have to claim the whole reward, but the coinbase TX must be included.



[1] https://www.blocktrail.com/BTC/block/42

[Amph]

Blocks are not required to have any transactions in them.

i'm curious about this aspect... but the number of transactions per block is based on what? it's random?

[shorena]

Blocks are not required to have any transactions in them.

i'm curious about this aspect... but the number of transactions per block is based on what? it's random?

Keep in mind that the below is only a reflection of the default settings from bitcoin core. Miners can write their own versions with different rules.

No its not random. Firstly the mining node must be aware of transactions otherwise the block will be "empty". That is only include the coinbase TX. The transactions get sort by priority and fee. They include "blockprioritysize" (default is 50000) byte worth of transactions into the block that have a high priortiy but no (or low) fee. They further fill the block up to "blockmaxsize" (default is 750000) bytes worth of transactions. Its also possible to set "blockminsize" (default is 0) to make sure the block has at least a certain size. If not enough TX are present blockminsize will not keep you from hashing.

Its here[1] in the source and here[2] are the default values for the settings.

[1] https://github.com/bitcoin/bitcoin/blob/master/src/miner.cpp
[2] https://en.bitcoin.it/wiki/Running_Bitcoin

[minerpumpkin]

large fees or short block time.

Short block time? No one actually defines the block time deliberately! Fees also don't affect the time between blocks at all! Miners just try to find a new block as fast as possible and as soon as they find one, they publish it. Waiting for more transactions would be very risky, because you would end up risking your block-reward!

[odolvlobo]

Blocks are not required to have any transactions in them.

i'm curious about this aspect... but the number of transactions per block is based on what? it's random?

It is up to the miner to decide on which transactions to include in the block. A miner is generally not going to leave out any transactions that pay a fee, but she might leave out those that don't. Most, but not all, miners follow the policies in Bitcoin Core. Another consideration is propagation time. Larger blocks take longer to propagate, and that can increase the chances of it becoming an orphan. So, a miner may prefer smaller blocks, such as those without any transactions.

[lordbtc]

There are actually blocks that have no transactions included. I think the payout then will be only 25 btc as there are no miners fees given to the miner

[uininPeter]

Theoretically blocks can be solved on the first attempt, and with the number of attempts happening every second, the time that a block can be solved in is very short. I wouldn't be surprised if that were the case here.

[Sheldor333]

I don't know why some blocks have just a few transaction and other 1000+, it is weird in my opinion but it does happen.

[tescomatty]

There are actually blocks that have no transactions included. I think the payout then will be only 25 btc as there are no miners fees given to the miner

Do you have examples of these? I cant imagine why there would be no transactions unless they were very early blocks.

[Josepht]

There are actually blocks that have no transactions included. I think the payout then will be only 25 btc as there are no miners fees given to the miner

Do you have examples of these? I cant imagine why there would be no transactions unless they were very early blocks.

Yeah, these things happen. It happens if blocks are found like 1 second after each other.

Btw OP, why do you have to ask that question? Every senior member is supposed to know this.

[minerpumpkin]

I don't know why some blocks have just a few transaction and other 1000+, it is weird in my opinion but it does happen.

Well the answer to your question has been outlined in several of the posts in this thread: It's called variance. Miners try to solve/find a block as fast as possible. It makes no sense for them to wait and include a given amount of transactions. Adding transactions only makes the block bigger (thus it becomes more likely for the block to become orphaned) and waiting for more transactions to come in has an incredibly negative EV.

[imamanandyou]

I don't know why some blocks have just a few transaction and other 1000+, it is weird in my opinion but it does happen.

Well the answer to your question has been outlined in several of the posts in this thread: It's called variance. Miners try to solve/find a block as fast as possible. It makes no sense for them to wait and include a given amount of transactions. Adding transactions only makes the block bigger (thus it becomes more likely for the block to become orphaned) and waiting for more transactions to come in has an incredibly negative EV.

What is an orphaned block? Is that one where there are several fringes and that block ends up on a fringe that gets left because another was solved first?

[odolvlobo]

What is an orphaned block? Is that one where there are several fringes and that block ends up on a fringe that gets left because another was solved first?

Two miners might find a block at the same time, and only one will eventually be on the longest chain. The other will be forgotten. The name "orphan" is a bit of a misnomer, because an orphan block has a parent but it has no child (or perhaps no grandchild).

[minerpumpkin]

I don't know why some blocks have just a few transaction and other 1000+, it is weird in my opinion but it does happen.

Well the answer to your question has been outlined in several of the posts in this thread: It's called variance. Miners try to solve/find a block as fast as possible. It makes no sense for them to wait and include a given amount of transactions. Adding transactions only makes the block bigger (thus it becomes more likely for the block to become orphaned) and waiting for more transactions to come in has an incredibly negative EV.

What is an orphaned block? Is that one where there are several fringes and that block ends up on a fringe that gets left because another was solved first?

Yep, that's basically it. Just like odolvlobo has also explained this happens when there are two valid blocks mined (mostly roughly at the same time) and it now comes down to the next block that's being mined to which chain (both chains are actually valid until this point) it gets added. The one that gets left out will now most likely be abandoned.