---
title: mMessageHeader
framework: IOKit
role: symbol
role_heading: Instance Property
platforms: [Mac Catalyst 18.4+, macOS 10.7+]
path: iokit/iovideodevicenotificationmessage/1503932-mmessageheader
---

# mMessageHeader

The mach message header.

## Declaration

```occ
mach_msg_header_t mMessageHeader;
```