Looking at this transaction, mempool.space says that it has fee rate of 1.01 sat/vB but its Accelerated fee rate is 446 sat/VB.

Until now, I have come across the term Effective fee rate which represents the fee rate of the group in the context of CPFP. However, what is the Accelerated fee rate?

1 Answer 1


I assume this is a transaction used to test the new Accelerator Service that mempool.space has been working on.

It is my understanding that mempool.space has been working on a transaction accelerator service. The service is supposed to allow users to pay for a higher confirmation priority of a specific transaction out of band (not on-chain). The transaction itself remains unchanged.

From what I hear, they have agreements in place with a large portion of the hashrate to facilitate the service. The fee is only collected on success and returned otherwise. The fee was announced to be shared among all participating pools and mempool.space, not just the successful pool.

  • Interesting. So it is out of Bitcoin protocol and Bitcoin Core node implementation? For example, like paying miners, say, in dollars outside the network, and then they include your transaction in the block even though the fee rate is very low (just enough to enter the mempool) and under normal circumstances it would not enter the block.
    – LeaBit
    Commented Dec 15, 2023 at 19:50
  • 1
    I guess it could be paid via Lightning as well
    – Murch
    Commented Dec 15, 2023 at 19:53
  • Yes, but still outside of "normal" Bitcoin fee/fee rate protocol.
    – LeaBit
    Commented Dec 15, 2023 at 19:54
  • Yes the payment is out of band. The transaction is unchanged and gets included in a block even while the transaction’s fees would not warrant inclusion in the block.
    – Murch
    Commented Dec 15, 2023 at 20:38
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    I am confused why you often ask to verify information that was already included in the answer and that you understood perfectly judging from how you ask for verification
    – Murch
    Commented Dec 15, 2023 at 20:39

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