[#node-CoinbaseTx-witness]
= xref:node.adoc[node]::xref:node/CoinbaseTx.adoc[CoinbaseTx]::witness
:relfileprefix: ../../
:mrdocs:

The first (and only) witness stack element of the coinbase input.

== Synopsis

Declared in `<node/mining_types.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
std::optional<uint256> witness;
----

== Description

Omitted for block templates without witness data.

This is currently the BIP 141 witness reserved value, and can be chosen arbitrarily by the node, but future soft forks may constrain it.


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