Does Bitcoin "confirmations" have nothing to do with fullnodes -- only miners?

Question

Roughly every 10 minutes, a new "block" is created. If Joe sends Sue a satoshi, it will be at least 9 minutes and 59 seconds until they get 1 confirmation (as I understand it). Then, subsequent blocks will increase the number of confirmations in perpetuity, with 6 blocks equating to roughly one hour.

But up until today, I always thought that "confirmations" were simply fullnodes (such as the non-pruned Bitcoin Core I'm running) "confirming" that the transaction took place.

Is this entirely false? If so, what is the point of my fullnode? Does it have any say/power whatsoever? It seems like the miners are the only ones who matter.

Answer 1

If Joe sends Sue a satoshi, it will be at least 9 minutes and 59 seconds until they get 1 confirmation (as I understand it).

This is not true. There is no fixed time interval between two blocks. You might see several blocks in a few minutes or no blocks for an hour. On average if looking at a bigger time frame, the block interval is ~10 minutes because of difficulty adjustments.

Then, subsequent blocks will increase the number of confirmations in perpetuity, with 6 blocks equating to roughly one hour.

Partially correct. Blocks mined after the first confirmation will increase a transaction's number of confirmations.

But up until today, I always thought that "confirmations" were simply fullnodes (such as the non-pruned Bitcoin Core I'm running) "confirming" that the transaction took place

1. Pruned nodes are also full nodes because they fully validate all blocks and transactions.

2. Full nodes do not add transactions to blocks. That is done by miners when they mine blocks.

If so, what is the point of my fullnode? Does it have any say/power whatsoever? It seems like the miners are the only ones who matter

1. Full nodes are used because you cannot trust others (verify all transactions yourself), privacy (not leak information about your transactions) and enforce consensus rules.

2. Miners are not the only ones who matter. Rather, if miners mine invalid blocks those get rejected by the full nodes.

Answer 2

Every fully verifying node checks locally whether the transactions and blocks adhere to the consensus rules of the network. It is important that nodes enforce the consensus rules themselves as they otherwise would need to trust their peers to give them correct information—which would be trivial to abuse. By running a full node, you guarantee that your view of the Bitcoin network's state is valid according to the consensus rules.

We call the inclusion of a transaction into a block by miners the first confirmation of a transaction. The reliability of a transaction due to being confirmed is only ever probabilistic, because a chaintip could get replaced by a competing chaintip with more work (to be clear, this rarely ever happens in practice). However, each subsequent block adds more proof of work to the chaintip and makes it harder to replace the block that included your transaction. Thus, we count more blocks being found after the block that confirmed a transaction as additional confirmations for that transaction.