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Today, I sent a Bitcoin payment but it has not been included in a block for about 10 hours now. The payment had the following characteristics:

  • ~0.1 BTC
  • 222 bytes
  • One UTXO as an input (I used coin control)
  • The UTXO was approximately 1 year old

Currently, blocks are not always full (in fact there are blocks that are only 8% full). For that reason I attempted to save the fee.

enter image description here

(https://bitcoinfees.github.io/#1m)

enter image description here

(https://blockchain.info/ 2016-08-08 20:42 UTC).

What policy do miners currently have regarding zero fee transactions? I have sent many zero fee transactions in the past (>1 year ago) and the block inclusion time was really quick (~5 blocks maybe). Did the policy of miners change?

  • In the last 6 blocks (screenshot) there are 4 that are significantly empty. It should be possible to include more data. Of course, including a zero fee transaction does not increase profits but in the past miners did it nonetheless as a public service. – boot4life Aug 8 '16 at 22:40
  • It just comes down to whichever valid block a miner finds first. A miner will find more blocks in general if they consider blocks of any size rather than just full. There are very often empty blocks with only the block reward transaction and nothing else. – Dylan James McGannon Aug 8 '16 at 23:00
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It likely has to do with the minimum relay fee set on the nodes that are mining. There's also coin age that is taken into consideration on low or no fee transactions.

Relay and Mining: Priority transactions

Bitcoin Core has a heuristic ‘priority’ based on coin value and age. This calculation is used for relaying of transactions which do not pay the minimum relay fee, and can be used as an alternative way of sorting transactions for mined blocks. Bitcoin Core will relay transactions with insufficient fees depending on the setting of -limitfreerelay= (default: r=15 kB per minute) and -blockprioritysize=.

Soure

  • A few lines later in the source you linked: "The mining of transactions based on their priority is also now disabled by default." – Murch Aug 9 '16 at 8:42
  • So I might find that the transaction will never take because all pools are configured to reject such a thing now? It would be interesting to see what zero-fee transactions were made in the past weeks. bitcoinfees.21.co says 302 in 24 hours. Those could be special purpose trans that are not available to the public. – boot4life Aug 9 '16 at 9:54
  • According to Gregory Maxwell there are no free transactions anymore: github.com/bitcoin/bitcoin/issues/8334#issuecomment-232278522 – boot4life Aug 9 '16 at 11:27

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