---
title: "Text box atom ('tbox')"
framework: quicktime-file-format
role: symbol
role_heading: Atom
path: quicktime-file-format/text_box_atom
---

# Text box atom ('tbox')

An atom that defines a text box for a subtitle sample.

## Overview

Overview This optional extension defines a text box for a subtitle sample, to be used as described in Sample extensions. If present, this overrides the default text box in the associated sample description. If the subtitle sample description’s Display flags do not include the Vertical Placement flag (0x20000000), the Text Box atom should not be included in any sample of the subtitle track.

## Topics

### Data fields

- [Size](quicktime-file-format/text_box_atom/size.md)
- [Type](quicktime-file-format/text_box_atom/type.md)
- [Text box](quicktime-file-format/text_box_atom/text_box.md)

## See Also

### Storing subtitles

- [Subtitle sample description](quicktime-file-format/subtitle_sample_description.md)
- [Font table atom ('ftab')](quicktime-file-format/font_table_atom.md)
- [Subtitle sample data](quicktime-file-format/subtitle_sample_data.md)
- [Subtitle style atom ('styl')](quicktime-file-format/subtitle_style_atom.md)
- [Subtitle track header size and placement](quicktime-file-format/subtitle_track_header_size_and_placement.md)
- [Referencing a related forced subtitle track](quicktime-file-format/referencing_a_related_forced_subtitle_track.md)