user119913: In a coinbase transaction the second transaction output seems always to be a 32-byte witness reserved value. Is there any constraint on this value?

user48884: The only constraint on this value is that it must be 32 bytes. Otherwise there are no constraints. This is done to allow for a future soft fork to commit to new data and have non-upgraded nodes still be able to store something in the block that commits to the new data. As such, the witness reserved value must remain unconstrained to allow for a future soft fork to work.

119913: <p>In a coinbase transaction the second transaction output seems always to be a 32-byte witness reserved value. Is there any constraint on this value?</p>
 48884: <p>The only constraint on this value is that it must be 32 bytes. Otherwise there are no constraints. This is done to allow for a future soft fork to commit to new data and have non-upgraded nodes still be able to store something in the block that commits to the new data. As such, the witness reserved value must remain unconstrained to allow for a future soft fork to work.</p>
