<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>

CC BY-SA 4.0
2021-04-25T18:02:35.577Z
2021-04-25T18:02:35.577Z
Ava Chow
<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>

<transactions><mining-theory><coinbase-transaction><witness-data>
How is the witness reserved value set in a coinbase transaction?
Andy
# How is the witness reserved value set in a coinbase transaction?

(Asked by: username_0 on 2021-04-25)

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?

**Tags:** transactions, mining-theory, coinbase-transaction, witness-data


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## 1 answers

### Answer by username_1 on 2021-04-25. Score: 3 | Accepted answer

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.


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