Generate Captions

You can either:

• Generate captions automatically on upload (recommended), or
• Generate captions later via the captions API.

Option 1: Generate Captions During Upload (Recommended)

When requesting an upload URL, include:

• generateCaptions: true
• optionally captionLanguages: ["en"]
• optionally captionTranslate: true (if you want translations generated)

This works with both:

• POST /videos/upload-url (direct upload), and
• POST /videos/upload (upload-from-URL)

Option 2: Generate Captions After Upload

List available captions

/videos/{assetId}/captions

Request generation for a language

/videos/{assetId}/captions

Example body:

{
  "lang": "en",
  "translate": false,
  "overwrite": false
}

Upload your own captions

/videos/{assetId}/captions/upload

Example body:

{
  "lang": "en",
  "format": "vtt",
  "content": "WEBVTT\n\n00:00.000 --> 00:02.000\nHello world\n",
  "overwrite": true
}

Getting a Playback URL for Captions

To obtain a URL you can hand to a player:

/videos/{assetId}/captions/{lang}

Response body:

{
  "url": "https://worker.antcdn.net/v1/{edgeKey}/captions/en.vtt"
}