[#node-BlockCreateOptions-block_reserved_weight]
= xref:node.adoc[node]::xref:node/BlockCreateOptions.adoc[BlockCreateOptions]::block&lowbar;reserved&lowbar;weight
:relfileprefix: ../../
:mrdocs:

The default reserved weight for the fixed&hyphen;size block header, transaction count and coinbase transaction&period; Minimum&colon; 2000 weight units (MINIMUM&lowbar;BLOCK&lowbar;RESERVED&lowbar;WEIGHT)&period;

== Synopsis

Declared in `&lt;node&sol;mining&lowbar;types&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
std::optional&lt;uint64&lowbar;t&gt; block&lowbar;reserved&lowbar;weight = &lcub;&rcub;;
----

== Description

Providing a value overrides the `&hyphen;blockreservedweight` startup setting&period; Cap&apos;n Proto IPC clients currently cannot leave this field unset, so they always provide a value&period;


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