Add captions

Adding captions and subtitles to your video library.

Add or modify a caption

There are two ways to add captions to a video: generating via AI or uploading a caption file.

To create or modify a caption on a video a Cloudflare API Token ↗ is required.

The <LANGUAGE_TAG> must adhere to the BCP 47 format ↗. For convenience, the most common language codes are provided at the bottom of this document. If the language you are adding isn’t included in the table, you can find the value through the The IANA registry ↗, which maintains a list of language codes. To find the value to send, search for the language. Below is an example value from IANA when we look for the value to send for a Turkish subtitle:

%%
Type: language
Subtag: tr
Description: Turkish
Added: 2005-10-16
Suppress-Script: Latn
%%

The Subtag code indicates a value of tr. This is the value you should send as the language at the end of the HTTP request.

A label is generated from the provided language. The label will be visible for user selection in the player. For example, if sent tr, the label Türkçe will be created; if sent de, the label Deutsch will be created.

Generate a caption

Generated captions use artificial intelligence based speech-to-text technology to generate closed captions for your videos.

A video must be uploaded and in a ready state before captions can be generated. In the following example URLs, the video’s UID is referenced as <VIDEO_UID>. To receive webhooks when a video transitions to ready after upload, follow the instructions provided here.

Only English language caption generation is currently supported.

Videos may include several language captions, but each language must be unique. For example, a video may have English, French, and German captions associated with it, but it cannot have two English captions. If you have already uploaded an English language caption for a video, you must first delete it in order to create an English generated caption. Instructions on how to delete a caption can be found below.

The <LANGUAGE_TAG> must adhere to the BCP 47 format. The tag for English is en. You may specify a region in the tag, such as en-GB, which will render a label that shows British English for the caption.

curl -X POST \
-H 'Authorization: Bearer <API_TOKEN>' \
https://api.cloudflare.com/client/v4/accounts/<ACCOUNT_ID>/stream/<VIDEO_UID>/captions/<LANGUAGE_TAG>/generate

Example response:

{
  "result": {
    "language": "en",
    "label": "English (auto-generated)",
    "generated": true,
    "status": "inprogress"
  },
  "success": true,
  "errors": [],
  "messages": []
}

The result will provide a status denoting the progress of the caption generation.
There are three statuses: inprogress, ready, and error. Note that (auto-generated) is applied to the label.

Once the generated caption is ready, it will automatically appear in the video player and video manifest.

If the caption enters an error state, you may attempt to re-generate it by first deleting it and then using the endpoint listed above. Instructions on deletion are provided below.

Upload a file

Note two changes if you edit a generated caption: the generated field will change to false and the (auto-generated) portion of the label will be removed.

To create or replace a caption file:

curl -X PUT \
 -H 'Authorization: Bearer <API_TOKEN>' \
 -F file=@/Users/mickie/Desktop/example_caption.vtt \
https://api.cloudflare.com/client/v4/accounts/<ACCOUNT_ID>/stream/<VIDEO_UID>/captions/<LANGUAGE_TAG>

Example Response to Add or Modify a Caption

{
  "result": {
    "language": "en",
    "label": "English",
    "generated": false,
    "status": "ready"
  },
  "success": true,
  "errors": [],
  "messages": []
}

List the captions associated with a video

To view captions associated with a video. Note this results list will also include generated captions that are inprogress and error status:

curl -H 'Authorization: Bearer <API_TOKEN>' \
https://api.cloudflare.com/client/v4/accounts/<ACCOUNT_ID>/stream/<VIDEO_UID>/captions

Example response to get the captions associated with a video

{
  "result": [
    {
      "language": "en",
      "label": "English (auto-generated)",
      "generated": true,
      "status": "inprogress"
    },
    {
      "language": "de",
      "label": "Deutsch",
      "generated": false,
      "status": "ready"
    }
  ],
  "success": true,
  "errors": [],
  "messages": []
}

Fetch a caption file

To view the WebVTT caption file, you may make a GET request:

curl \
-H 'Authorization: Bearer <API_TOKEN>' \
https://api.cloudflare.com/client/v4/accounts/<ACCOUNT_ID>/stream/<VIDEO_UID>/captions/<LANGUAGE_TAG>/vtt

Example response to get the caption file for a video

WEBVTT

1
00:00:00.000 --> 00:00:01.560
This is an example of

2
00:00:01.560 --> 00:00:03.880
a WebVTT caption response.

Delete the captions

To remove a caption associated with your video:

curl -X DELETE \
 -H 'Authorization: Bearer <API_TOKEN>' \
 https://api.cloudflare.com/client/v4/accounts/<ACCOUNT_ID>/stream/<VIDEO_UID>/captions/<LANGUAGE_TAG>

If there is an entry in errors response field, the caption has not been deleted.

Example response to delete the caption

{
  "result": "",
  "success": true,
  "errors": [],
  "messages": []
}

Limitations

• A video must be uploaded before a caption can be attached to it. In the following example URLs, the video’s ID is referenced as media_id.
• Stream only supports WebVTT ↗ formatted caption files. If you have a differently formatted caption file, use a tool to convert your file to WebVTT ↗ prior to uploading it.
• Videos may include several language captions, but each language must be unique. For example, a video may have English, French, and German captions associated with it, but it cannot have two French captions.
• Each caption file is limited to 10 MB in size. Contact support if you need to upload a larger file.

Most common language codes

Language Code	Language
zh	Mandarin Chinese
hi	Hindi
es	Spanish
en	English
ar	Arabic
pt	Portuguese
bn	Bengali
ru	Russian
ja	Japanese
de	German
pa	Panjabi
jv	Javanese
ko	Korean
vi	Vietnamese
fr	French
ur	Urdu
it	Italian
tr	Turkish
fa	Persian
pl	Polish
uk	Ukrainian
my	Burmese
th	Thai