Earlier today I submitted a transaction on the Testnet. Shortly after I checked it using blockfrost and got the info my tx is included in block 3681998

A few hours later I checked again, but now the tx is included in block 3682001.

I am seeking for an explanation how that happened.

Thank you!

2 Answers 2


My suspicion is as follows:

  • You saw the tx in block 3681998 (which must have been the chain tip).
  • Another block (competing with 3681998) was chosen by the consensus algorithm that did not contain that tx.
  • Block 3682001 was added that included that tx.
  • Thanks for your answer. Maybe that's what happened. Did you notice block 3681998 is empty? How can I check if the block wasn't chosen?
    – LACE pool
    Jul 5 at 13:20
  • Sometimes there are empty blocks. There is no way to check why a block wasn't chosen. This is the normal operation of a distributed ledger / blockchain. Read up on how bitcoin chooses blocks. Jul 5 at 14:29

The latest blocks in the blockchain generally can change for a while until further blocks are created on top and push your transaction down the chain. The "deeper" it gets, the more likely it is not to change.

The two blocks you're pointing to are just ~3 minutes apart, so there doesn't seem to be anything abnormal about it. Here's a good read on these confirmation times / settlement windows.

  • Thanks for your quick response! I should have added to my question that I am aware blocks only become truly immutable after 129600 slots. My question is more about how this specific case occurred. Sorry if I wasn't clear.
    – LACE pool
    Jul 5 at 9:23
  • 2
    Ah okay, I don't know of a way to get the data for this specific case unfortunately. But the first block holding your transaction was probably orphaned for a reason that is described nicely in this article: beaver-stake-pool.net/post/…
    – sean
    Jul 5 at 18:55

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