Bitcoin Forum

Does the number of confirmations keep increasing until eternity or is there any certain max? I've seen transactions from years ago have 30K confirmations. But what is the record actually?

AFAIK the number of confirmations is just how many blocks are ahead of the transaction.

For example, if the tx was included on block 50000, if we finally mine block 51000, it will have 1000 confirmations. So, someone would need to reorg the 1000 blocks to "undo" the transaction.

But still, what is the highest number of confirmations you have ever seen? Or know of that somebody reported to have seen?

Bitcoin's first transaction?

I know Hal Finney's first transaction, which was included on block 170 and has 597017 confirmations.

https://live.blockcypher.com/btc/tx/f4184fc596403b9d638783cf57adfe4c75c605f6356fbc91338530e9831e9e16/

Interesting! Thanks, was just curious.

a better term to describe that number is "depth" instead of number of confirmation. it says it all, when you see a tx that has 30k confirmation, it means it is 30k blocks deep from the head. so if for example the head is at block height 10 and your tx is in that block, your confirmation is 1 meaning it is 1 block deep. when there are more blocks found and we reach block 15, your tx has 5 confirmation and it means it is 5 blocks deep.

what is the most number of confirmation? it is equal to number of blocks we have at that time (plus 1*).
last block's height: 597211†
tx with highest number of confirmation (597212†): https://blockchair.com/bitcoin/transaction/4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b

* the reason for +1 is because the very first transaction is the genesis block's coinbase tx which is in block #0
† these numbers could be different by the time you look at them since the blockchain is constantly growing.

Technically a bitcoin transaction is never final, it just has increasing amounts of finality that goes up with it's depth on the blockchain.

So in that perspective, a bitcoin transaction is constantly adding more and more confirmations, that translate to more and more finality.

For most people, beyond a certain number, such as 1 or 6, it's as good as it gets. That tx is already included in a block and will likely never be reversed. The more confirmations pass, the more "secure" it is. 6 is estimated to take an hour, so think of it like a check that clears in an hour.

In some other countries, banks wait 3 days before they clear a check or even a bank draft. If you had a bitcoin transaction and it confirmed 3 days ago, you can be sure that no one is going to ever reverse that. For all practical intents and purposes it's final. You can move or spend it or whatever you want to do with it. The number of confirmations beyond 100 or 1000 is meaningless for anyone but those interested in the technical details.

You buy a coffee, 1 confirmation may be good enough, or if paid through lightning there isn't even a confirmation until the channel is settled on chain.

You bought land or a car, 6 confirms may be good. 10 is better but no point beyond that even for a million dollars worth. There are other kinds of "transactions" like if you gave the seller a loaded OpenDime, and he gave you the car keys after.

The number of confirmation does not make sense once they exceed safe limits but the definition of safe limits is different from one transaction to another:

 - If you trust the other party and the transaction value up to $100 worth, 0/unconfirmed may be sufficient once the transaction is broadcast.
 - For trades between people who are unknown or do not expect to meet again, 3 confirmations are considered safe.
 - 6 confirmations are sufficient for many transactions but even this number of confirmations are not considered 100% safe. Read more ---> A successful DOUBLE SPEND US$10000 against OKPAY this morning. (https://bitcointalk.org/index.php?topic=152348.0)

Generally, these safe limits varies from one cryptocurrency to another.

The double spend from March 2013 was a particularly odd case with an accidental hard fork due to the 0.7 and 0.8 upgrade.  If you want to read more, there is a lot out there, but barring something like this, 6 confirmations is usually sufficient, but if you are running a service like OKPAY, then monitoring the network status is important.  And perhaps keeping at least two different versions of Bitcoin Core running on different nodes to ensure they are in agreement.

these numbers are not absolute. it depends on 3 things: (1) amount being transferred (2) state of the network and (3) your method of accessing the blockchain.
you already talked about (1) but not the other.
2) state of the network means if there was some sort of issue, reorg, fork,... that needed extra attention. during these times the number of confirmation required to be safer increases depending on the issue. it can even go up to 100.
3) this basically means whether you are using a full node or a light client. if for example you are using an SPV wallet then you should wait for higher number of confirmation under all circumstances which will grow more if there was an issue.

Do you mind expanding on this for me? Was it an accident or is there any specifics/details I could comb over that you might know about?

Check this one "Analyzing the 2013 Bitcoin fork: centralized decision-making saved the day (https://freedom-to-tinker.com/2015/07/28/analyzing-the-2013-bitcoin-fork-centralized-decision-making-saved-the-day/)"

This might be the article you are looking for.

Or check this one "Bitcoin Network Shaken by Blockchain Fork (https://bitcoinmagazine.com/articles/bitcoin-network-shaken-by-blockchain-fork-1363144448)"

You're buying a cup of coffee. Merchant can probably accept even zero conf, or is already using second layer Lightning or even some payment processor.

You're buying a car. Seller can probably wait a few minutes before giving the car keys. Maybe even accept the transaction, do some other things to the car, vacuum and clean it. By the time that's done, there will be a number of confirmations already. It's a car, it's registered. There's paperwork.

You're buying a house. Realtor accepts transactions, says, "come back tomorrow" for the keys and inspection report and all the old bills which will have to be changed to your name, like electric, cable, water, mortgage, whatever. By tomorrow, there are hundreds of confirmations.

It's a house. It's not going to move. (I've seen houses move with giant trucks, but that's another story.)