Somewhere around 2016-2017, i witnessed people creating 0 fee transactions and getting them confirmed. As long as a single miner runs an old node, a patched node or an alternative node (like btcd) that is configured to accept and relay 0 fee transactions, AND still uses the old, deprecated priority mechanism you can always try to setup a patched node and connect directly to this mining node, then create a 0 fee transaction and get it broadcasted to this miner's node...
However, at this point in time, you'd need very specific and detailed info about which miners would be running such a patched and alternatively-configured node, my guess would be there aren't many of those miners left.
And in the odd chance you do get a 0 fee transaction in his/her node's mempool, and your transaction has very high priority (and the miner still reserves a space in his/her block for high priority transactions), the miner would still need to find a block header whose hash is under the current target (ie solve the block).
Odds are small, very, very, small... But i don't think they're absolute 0.
I imagine about some problems with 0-fee transactions:
- How long does it take to get confirmations?
- With today very high dificulty of bitcoin, if someone set up his/her node and do some technical steps to try luck and get 0-fee transactions, I think it sounds very crazy.
[1] Time always make sense. One can send coins and wait for hours or days but too long waiting time does not a comfortable thing to suffer.
According to
https://whatthefee.io/, at the current status of bitcoin network, 3 satoshis/ byte is the most comfortable fee (corresponds to acceptable waiting time) to move coins.
I think one can carefully check suggested fees before moving coins but most of time, I move my coins at 1 satoshi/byte and it works smooth.
Beyond that, I know the expiration time of unconfirmed transactions is 72 hours (3 days)
[3]. Waiting 3 days, and repeat 0-fee transactions, then wait for luck again sounds very crazy.
[2] If one can be able to set up patched node, then miner's node, I don't see the difference between 0-fee or 1-satoshi/byte transactions for them to spend time (to setup and wait) for luck (too) to get 0-fee transactions.
[3] https://hackernoon.com/holy-cow-i-sent-a-bitcoin-transaction-with-too-low-fees-are-my-coins-lost-forever-7a865e2e45ba
I'm interested, I used to be able to consolidate inputs for free, and I didn't mind waiting a day or two if I did not need to spend them otherwise.
If three days pass and your transactions don't get confirmations, you have to repeat free-consolidated transactions again.
Otherwise we just stick to 1 sat, and that's still fine.
I think 1 satoshi/byte transaction is fine enough.
What % of chances are there of a 0 sat/byte fee transaction to get relayed through a node allowing such 0 fee transactions these days if mempool has got a very big amount of transactions stuck at that level?
If 0 satoshi/byte transaction is realistic, I think there are sites suggest it already. I have never seen 0 satoshi/byte transactions suggested by
https://whatthefee.io/ or
https://coinb.in/#fees