---
layout: stdlib-reference
---

# attribute [vk::constant\_id]

## Description

Mark a global variable as a Vulkan specialization constant.

## Signature

<pre>
[vk::constant_id(<a href="vk_constant_id.html#decl-location" class="code_param">location</a> : <span class="code_keyword">int</span>)]
</pre>

## Parameters

####  <a id="decl-location"></a>location  : int
The index of the specialization constant.