I read the original Bitcoin paper and think I understand it but I'm having a hard time relating it to the transaction pages on blockchain.info. For example, sometimes there are 2 outputs and neither of them is back to the sender (what the paper would call "change") which seems to violate the rules of splitting and combining described in the paper.

Is there a good guide on how to read these diagrams?


2 Answers 2


Change for a transaction doesn't have to go back to the original address: part of it can be sent to the receiver, and the other part can go back to a new address. That way it's slightly harder to trace where the money went, as you don't know which part was the transfer and which part was the change.


The rules are pretty simple:

  • there are one or more inputs to a transaction
  • there are zero or more outputs to a transaction
  • any difference between the input and the output values is treated as a transaction fee and kept by whomever mined the block

In terms of a "change" address, it is simply another output. It just happens to be one to an address to which you hold the private key. As to if that address has already been used for something else, that's up to whatever software generated the transaction.

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