v31

latestOpenAPI 3.1.0raw.githubusercontent.com2026-05-28124212862.9 KB

Assets

Create an asset track

Adds an asset track (for example, subtitles, or an alternate audio track) to an asset. Assets must be in the ready state before tracks can be added.

post/video/v1/assets/{ASSET_ID}/tracks

Path parameters

ASSET_IDstring required

The asset ID.

Request body

urlstring required

The URL of the file that Mux should download and use.

For audio tracks, the URL is the location of the audio file for Mux to download, for example an M4A, WAV, or MP3 file. Mux supports most audio file formats and codecs, but for fastest processing, you should use standard inputs wherever possible.
For text tracks, the URL is the location of subtitle/captions file. Mux supports SubRip Text (SRT) and Web Video Text Tracks formats for ingesting Subtitles and Closed Captions.

type'text' | 'audio' required

text_type'subtitles'

language_codestring required

The language code of this track. The value must be a valid BCP 47 specification compliant value. For example, en for English or en-US for the US version of English.

namestring

The name of the track containing a human-readable description. This value must be unique within each group of text or audio track types. The HLS manifest will associate the text or audio track with this value. For example, set the value to "English" for subtitles text track with language_code as en-US. If this parameter is not included, Mux will auto-populate a value based on the language_code value.

closed_captionsboolean

Indicates the track provides Subtitles for the Deaf or Hard-of-hearing (SDH).

passthroughstring

Arbitrary user-supplied metadata set for the track either when creating the asset or track.

Response

Created