I was wondering if I can add dummy data into a coinbase transaction’s inputs. Is it possible to do this? Can you insert invalid input scripts into a coinbase transaction? Can you add multiple inputs scripts into a coinbase, do they all have to be legit scripts, if they do open inputs does the coinbase transaction send more than the regular block reward?

1 Answer 1


Coinbase transactions must:

  • Have exactly 1 input.
  • That input must have prevout hash 0000...0000, and index 0xFFFFFFFF (an output which isn't actually spent).
  • The input's scriptSig must be between 2 and 100 bytes long.
  • Post BIP34 (2012), the scriptSig must start with a push of the block height in little endian encoding.
  • Be the first transaction in a block.

If it doesn't satisfy all these rules, the transaction, and the block it is in, are invalid.


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