---
title: "Movie data atom ('mdat')"
framework: QuickTime File Format
role: symbol
role_heading: Atom
path: quicktime-file-format/movie_data_atom
---

# Movie data atom ('mdat')

An atom that contains movie data.

## Overview

Overview As with the free and skip atoms, the movie data atom is structured quite simply. It consists of an atom header (atom size and type fields), followed by the movie’s media data. Your application can understand the data in this atom only by using the metadata stored in the movie atom. This atom can be quite large, and may exceed 2^32 bytes, in which case the size field will be set to 1, and the header will contain a 64-bit extended size field.

## Topics

### Data fields

- [Size](quicktime-file-format/movie_data_atom/size.md)
- [Type](quicktime-file-format/movie_data_atom/type.md)
- [Extended size](quicktime-file-format/movie_data_atom/extended_size.md)
- [Movie media data](quicktime-file-format/movie_data_atom/movie_media_data.md)