This is something that has puzzled me for a while and I cannot think of a rational reason for it. The transaction 3361d2484f0566ab13d32f2ab321319945f48eaea1ac2cc9f5a79b40528359c3 shows properly on blockchain.info and tradeblock.

However, I cannot find it either on blockr.io nor blocktrail.com.— I am also running a server to watch transactions and I cannot find this transaction either. Sometimes I can find transactions that do not appear on blockchain so it's quite random.

All servers have many connections so I wonder what could be the issue? Slow network?

  • 1
    You should mention in your question that the transaction is unconfirmed. Perhaps you could put screenshots, because the question will likely not be understandable once the transaction confirms.
    – Murch
    Feb 11, 2017 at 20:42
  • Nevermind, I took care of that in my answer. ;)
    – Murch
    Feb 11, 2017 at 21:10

1 Answer 1


Each node on the network has its own mempool. While they are filled with similar transactions, each may have a different size limit or perhaps even custom rules which transactions to retain.

Unconfirmed inputs

In this particular case you can see (figure 1) that there is a (U) shown in both inputs of the transaction. The (U) means that the inputs are created by a transaction that is still unconfirmed.

Address the inputs come from

In fact, when you look at the address that the two inputs were spent to before (figure 2), you'll see that both were created in transactions that only paid 4.4 satoshis per byte whereas the transaction you linked pays 65 satoshis per byte.

I would surmise that the first two transactions that created the inputs might have not been relayed to or were not kept in the mempool of the other blockexplorers. Then, the transaction that you linked would seem invalid to those blockexplorers, because the referenced inputs are not known to it.

You may find this related question interesting: "How do transactions leave the memory pool?"

  • Oh, I just see that I made German screenshots. "Unbestätigte Transaktion" means unconfirmed transaction as you probably have guessed.
    – Murch
    Feb 11, 2017 at 20:59
  • Thanks Murch - I did notice the inputs were unconfirmed but that does not explain why the transaction is not shown on some.
    – Alex
    Feb 11, 2017 at 21:13
  • May I just add that I am not seeing the transaction on my node, yet the mempool info shows that it's pretty empty: { "size": 12590, "bytes": 26220930, "usage": 52775360, "maxmempool": 300000000, "mempoolminfee": 0.00000000 } Is there anything else I need to do in order for this transaction to be included on my node?
    – Alex
    Feb 11, 2017 at 21:30
  • 1
    @Alex: Your node would only get the transaction if one of your peers relays it to you. If none of your peers has it, you'll still not see it even if your node would be permissive enough to show it.
    – Murch
    Feb 11, 2017 at 21:48

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