# PFN_vkDebugUtilsMessengerCallbackEXT(3) Manual Page

## Name

PFN_vkDebugUtilsMessengerCallbackEXT - Application-defined debug messenger callback function

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## C Specification

The prototype for the VkDebugUtilsMessengerCreateInfoEXT::`pfnUserCallback` function implemented by the application is:

    // Provided by VK_EXT_debug_utils
    typedef VkBool32 (VKAPI_PTR *PFN_vkDebugUtilsMessengerCallbackEXT)(
        VkDebugUtilsMessageSeverityFlagBitsEXT           messageSeverity,
        VkDebugUtilsMessageTypeFlagsEXT                  messageTypes,
        const VkDebugUtilsMessengerCallbackDataEXT*      pCallbackData,
        void*                                            pUserData);

## Parameters

- `messageSeverity` specifies the VkDebugUtilsMessageSeverityFlagBitsEXT that triggered this callback.

- `messageTypes` is a bitmask of VkDebugUtilsMessageTypeFlagBitsEXT specifying which type of event(s) triggered this callback.

- `pCallbackData` contains all the callback related data in the VkDebugUtilsMessengerCallbackDataEXT structure.

- `pUserData` is the user data provided when the VkDebugUtilsMessengerEXT was created.

## Description

The callback returns a VkBool32, which is interpreted in a layer-specified manner. The application should always return `VK_FALSE`. The `VK_TRUE` value is reserved for use in layer development.

Valid Usage

- VUID-PFN_vkDebugUtilsMessengerCallbackEXT-None-04769
  The callback must not make calls to any Vulkan commands

## See Also

VK_EXT_debug_utils, VkDebugUtilsMessageSeverityFlagBitsEXT, VkDebugUtilsMessageTypeFlagsEXT, VkDebugUtilsMessengerCallbackDataEXT, VkDebugUtilsMessengerCreateInfoEXT

## Document Notes

For more information, see the Vulkan Specification

This page is extracted from the Vulkan Specification. Fixes and changes should be made to the Specification, not directly.

## Copyright

Copyright 2014-2025 The Khronos Group Inc.

SPDX-License-Identifier: CC-BY-4.0