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It's known the txid is always a 32 byte hex sequence for example ceca9c54d1a2f9122326a871a3b0b20b725540137e80cb50da663a404f7849a8, but when inpecting the transaction in a wallet it shows it with a dash and three number postfix :
What does -000 mean in the txid, and why is it there?
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It means this receive is due to output number 0 of the listed transaction.
Transactions can have multiple outputs (and usually do), and it is possible that more than one of them pays you. If that is the case, they will be listed as separate "transactions" in the UI, but their output will be distinct.
so, does it means that 00 is the index of vout in the raw transaction? – Ben – 2018-08-27T17:13:39.373
Correct, that's it. – Pieter Wuille – 2018-08-27T19:57:38.753