---
title: "Handler reference atom ('hdlr')"
framework: quicktime-file-format
role: symbol
role_heading: Atom
path: quicktime-file-format/handler_reference_atom
---

# Handler reference atom ('hdlr')

An atom that specifies the media handler component that is to be used to interpret the media’s data.

## Overview

Overview The handler reference atom has an atom type value of 'hdlr'. Historically, the handler reference atom was also used for data references. However, this isn’t the case anymore. The handler atom within a media atom declares the process by which the media data in the stream may be presented, and thus, the nature of the media in a stream. For example, a video handler would handle a video track. The layout of a handler reference atom is as follows.  |   |   |   |   |   |   |   |   |   |   |

## Topics

### Data fields

- [Size](quicktime-file-format/handler_reference_atom/size.md)
- [Type](quicktime-file-format/handler_reference_atom/type.md)
- [Version](quicktime-file-format/handler_reference_atom/version.md)
- [Flags](quicktime-file-format/handler_reference_atom/flags.md)
- [Component type](quicktime-file-format/handler_reference_atom/component_type.md)
- [Component subtype](quicktime-file-format/handler_reference_atom/component_subtype.md)
- [Component manufacturer](quicktime-file-format/handler_reference_atom/component_manufacturer.md)
- [Component flags](quicktime-file-format/handler_reference_atom/component_flags.md)
- [Component flags mask](quicktime-file-format/handler_reference_atom/component_flags_mask.md)
- [Component name](quicktime-file-format/handler_reference_atom/component_name.md)

## See Also

### Describing media

- [Media atom ('mdia')](quicktime-file-format/media_atom.md)
- [Media header atom ('mdhd')](quicktime-file-format/media_header_atom.md)
- [Extended language tag atom ('elng')](quicktime-file-format/extended_language_tag_atom.md)
- [Media information atoms](quicktime-file-format/media_information_atoms.md)
- [Video media information atom ('minf')](quicktime-file-format/video_media_information_atom.md)
- [Video media information header atom ('vmhd')](quicktime-file-format/video_media_information_header_atom.md)
- [Sound media information atom ('minf')](quicktime-file-format/sound_media_information_atom.md)
- [Sound media information header atom ('smhd')](quicktime-file-format/sound_media_information_header_atom.md)
- [Base media information atom ('minf')](quicktime-file-format/base_media_information_atom.md)
- [Base media information header atom ('gmhd')](quicktime-file-format/base_media_information_header_atom.md)
- [Base media info atom ('gmin')](quicktime-file-format/base_media_info_atom.md)
- [Data information atom ('dinf')](quicktime-file-format/data_information_atom.md)
- [Data reference atom](quicktime-file-format/media_data_reference_atom.md)