Extend an Existing Video

April 18, 2025

Table of contents

  1. Request Headers
  2. Request Body
  3. Responses
  4. Model
  5. Examples
  6. Try It

This endpoint extends a previously generated video, continuing the animation from where it left off.

https://api.useapi.net/v1/kling/videos/extend

Request Headers 
Authorization: Bearer {API token}
Content-Type: application/json
# Alternatively you can use multipart/form-data
# Content-Type: multipart/form-data
Request Body 
{
  "email": "[email protected]",
  "task_id": "12345678",
  "prompt": "Continue with the mountain landscape, now showing a sunset",
  "negative_prompt": "people, low quality, distorted",
  "cfg_scale": 0.5,
  "replyUrl": "https://your-callback-url.com/webhook",
  "replyRef": "your-reference-id"
}

  • email is optional when only one account configured.
    However, if you have multiple accounts configured, this parameter becomes required.

  • task_id is required, the ID of a completed video generation task to extend.
    You can get a list of your tasks from GET /tasks.

  • prompt is optional, text description to guide the extended video generation.
    Maximum length: 2500 characters.

  • negative_prompt is optional, what not to include in the generated video.
    Maximum length: 2500 characters.

  • cfg_scale is optional, guidance scale for video extension.
    Range: 0 to 1. Default: 0.5.

  • maxJobs is optional, range from 1 to 10.
    Specifies the maximum number of concurrent jobs.

  • replyUrl is optional, a callback URL to receive results when completed.

  • replyRef is optional, a reference identifier for the callback.

Note: The task specified by task_id must be in the succeed status for the extension to work.

Responses

  • 200 OK

    {
  "id": 87654321,
  "created": 1712345678000,
  "status": "submitted",
  "status_final": false,
  "type": "m2v_extend_video",
  "taskInfo": {
    "inputs": [
      {
        "name": "input",
        "url": "https://s21-kling.klingai.com/video12345.mp4",
        "fromWorkId": 12345678
      }
    ],
    "arguments": [
      {
        "name": "prompt",
        "value": "Continue with the mountain landscape, now showing a sunset"
      },
      {
        "name": "negative_prompt",
        "value": "people, low quality, distorted"
      },
      {
        "name": "cfg",
        "value": 0.5
      },
      {
        "name": "__initialType",
        "value": "m2v_txt2video_hq"
      },
      {
        "name": "__initialPrompt",
        "value": "A majestic mountain landscape with snow-capped peaks and flowing rivers"
      },
      {
        "name": "kling_version",
        "value": "1.6"
      }
    ]
  },
  "scheduled": true
}

  • 400 Bad Request

    {
  "error": "Task is not completed"
}

  • 401 Unauthorized

    {
  "error": "Unauthorized",
  "code": 401
}

When successful, the response includes a task ID which can be used to check the status using GET /tasks/{task_id}.

Model 
{ // TypeScript, all fields are optional
  id: number          // Task ID
  created: number     // Creation timestamp in milliseconds
  status: string      // Task status: "submitted", "processing", "failed", or "succeed"
  status_final: boolean // Whether this is the final status of the task
  type: string        // Task type, typically "m2v_extend_video"
  taskInfo: {
    inputs: Array<{
      name: string    // Input name
      url: string     // Input URL
      fromWorkId: number // Original task ID
    }>
    arguments: Array<{
      name: string    // Argument name
      value: string   // Argument value
    }>
  }
  scheduled: boolean  // Whether the task is scheduled
}
Examples 
  • curl -X POST "https://api.useapi.net/v1/kling/videos/extend" \
   -H "Content-Type: application/json" \
   -H "Authorization: Bearer …" \
   -d '{
     "email": "[email protected]",
     "task_id": "12345678",
     "prompt": "Continue with the mountain landscape, now showing a sunset",
     "negative_prompt": "people, low quality, distorted"
   }'

  • const token = "API token";
const email = "Previously configured account email";
const apiUrl = "https://api.useapi.net/v1/kling/videos/extend"; 
const response = await fetch(apiUrl, {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "Authorization": `Bearer ${token}`,
  },
  body: JSON.stringify({
    email: email,
    task_id: "12345678",
    prompt: "Continue with the mountain landscape, now showing a sunset",
    negative_prompt: "people, low quality, distorted"
  })
});
const result = await response.json();
console.log("response", {response, result});

  • import requests
token = "API token"
email = "Previously configured account email"
apiUrl = "https://api.useapi.net/v1/kling/videos/extend"
headers = {
    "Content-Type": "application/json", 
    "Authorization" : f"Bearer {token}"
}
data = {
    "email": email,
    "task_id": "12345678",
    "prompt": "Continue with the mountain landscape, now showing a sunset",
    "negative_prompt": "people, low quality, distorted"
}
response = requests.post(apiUrl, headers=headers, json=data)
print(response, response.json())
Try It