Udio Extend API: Follow-up Action

POST /v2/music/udio/action — action: "extend"

Equivalent to Udio's Extend button: adds a new section to one of the parent job's songs, either before it or after it. The result is a fresh pair of songs — same shape as a generation — and each can be extended again, which is how you build a track longer than Udio's 130-second maximum.

One extension per call, and at most 32 seconds of new audio, because Udio renders one 32-second sample at a time. Chaining is deliberate: you hear each section before deciding what comes next.

Select the song with index (1 or 2) or with the trackId from the parent's result.tracks[].id — exactly one of the two.

Request

Parameter	Type	Required	Description
`parentJobId`	string (uuid)	Yes	ID of the completed udio job to act on
`action`	string	Yes	`"extend"`
`index`	number	One of `index`/`trackId`	Which of the parent's songs to extend: `1` or `2`
`trackId`	string	One of `index`/`trackId`	Song ID from the parent's `result.tracks[].id`
`placement`	string	No	Where the new section goes: `"after-add-section"`, `"after-add-outro"`, `"before-add-section"`, `"before-add-intro"`
`output_length`	number	No	Seconds of new audio, 1–32. Defaults to Udio's own choice
`prompt`	string	No	Description of the new material (max 5,000 characters). Defaults to the source song's
`lyrics`	string	No	Your own words for the new section (max 5,000 characters)
`lyrics_prompt`	string	No	What the new section should be about — Udio writes the lyrics from it (max 2,000 characters)
`lyrics_type`	string	No	`"generate"`, `"user"` or `"instrumental"`
`negative_tags`	string	No	Styles to avoid (max 500 characters)
`model`	string	No	Model version for the extension. Defaults to the source song's
`voice`	object	No	A reference voice
`style_ref`	object	No	A reference style
`bpm`	number	No	Target tempo, 60–200
`seed`	integer	No	Seed for reproducibility
`prompt_strength`	number	No	0–1
`lyrics_strength`	number	No	0–1
`clarity_strength`	number	No	0–1
`generation_quality`	number	No	0–1
`webhookUrl`	string	No	HTTPS URL that receives a JSON `POST` when the job reaches a subscribed event — see Webhooks for payload formats
`webhookEvents`	string[]	No	Events to be notified about: `"progress"`, `"completed"`, `"failed"`. Defaults to `["completed", "failed"]` when `webhookUrl` is set

Everything you leave out is inherited from the source song, so a bare request just continues what is already there.

Two limits are Udio's, not ours, and both are rejected before any credits are deducted:

Songs generated with a udio130-* model cannot be extended. Override model with a udio32-* one, or remix instead (400).
Songs longer than 15 minutes cannot be extended (409).

Credits

3 credits per extend — one 32-second sample, whatever the length of the source song.

Example result

Once the job is COMPLETED, the result object on GET /v2/jobs/:id contains a fresh pair of songs:

{
  "tracks": [
    {
      "id": "2c9a7e51-8f4b-4d3a-b6e0-1f5d8c2a9b74",
      "audioUrl": "https://cdn2.apiframe.ai/audio/d4e5f6a7-b8c9-0123-def4-567890123456-0.mp3",
      "imageUrl": "https://cdn2.apiframe.ai/audio/d4e5f6a7-b8c9-0123-def4-567890123456-0.jpeg",
      "title": "Midnight Frequencies",
      "tags": "lo-fi, hip hop, chill",
      "duration": 48.6
    },
    {
      "id": "7e3b1d96-2a5c-4f8e-9c07-4b6a1e8d3f25",
      "audioUrl": "https://cdn2.apiframe.ai/audio/d4e5f6a7-b8c9-0123-def4-567890123456-1.mp3",
      "imageUrl": "https://cdn2.apiframe.ai/audio/d4e5f6a7-b8c9-0123-def4-567890123456-1.jpeg",
      "title": "Midnight Frequencies",
      "tags": "lo-fi, hip hop, chill",
      "duration": 48.2
    }
  ]
}

Each of these songs can be the parent of another extend.

Code examples

curl -X POST https://api.apiframe.ai/v2/music/udio/action \
  -H "X-API-Key: afk_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "parentJobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "action": "extend",
    "index": 1
  }'

import requests

response = requests.post(
    "https://api.apiframe.ai/v2/music/udio/action",
    headers={
        "X-API-Key": "afk_your_api_key_here",
        "Content-Type": "application/json",
    },
    json={
        "parentJobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
        "action": "extend",
        "index": 1,
    },
)
print(response.json())

const response = await fetch("https://api.apiframe.ai/v2/music/udio/action", {
  method: "POST",
  headers: {
    "X-API-Key": "afk_your_api_key_here",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    parentJobId: "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    action: "extend",
    index: 1,
  }),
});
console.log(await response.json());

body := `{
  "parentJobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "action": "extend",
  "index": 1
}`
req, _ := http.NewRequest("POST", "https://api.apiframe.ai/v2/music/udio/action",
    strings.NewReader(body))
req.Header.Set("X-API-Key", "afk_your_api_key_here")
req.Header.Set("Content-Type", "application/json")

resp, err := http.DefaultClient.Do(req)

Add a 16-second outro with your own lyrics

curl -X POST https://api.apiframe.ai/v2/music/udio/action \
  -H "X-API-Key: afk_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "parentJobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "action": "extend",
    "trackId": "8b2f64d1-3c5e-4a7f-9d2b-6e1a0c4f8b3d",
    "placement": "after-add-outro",
    "output_length": 16,
    "lyrics": "[Outro]\nCity fades into the dawn"
  }'

Add an intro instead

curl -X POST https://api.apiframe.ai/v2/music/udio/action \
  -H "X-API-Key: afk_your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
    "parentJobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "action": "extend",
    "index": 1,
    "placement": "before-add-intro",
    "output_length": 8,
    "lyrics_type": "instrumental"
  }'

Try it

POST/v2/music/udio/actionTry it

API Key

Request Body (JSON)

Extend