POST gen4/act-two-voice

Create Act-Two voice swap

September 8, 2025

Request Headers
Request Body
Responses
Model
Examples
Try It

Runway Generate Video » Gen-4 or Gen-4 Turbo » Act-Two.

Please be aware that Runway’s moderation system analyzes your video assets and may fail task with moderation message if the content is determined to be offensive. Runway monitors the rate and the number of moderated tasks, which may result in your account being suspended when the internal threshold is exceeded.

The account you use to upload asset(s) via POST /assets will also be used to execute the generation. Uploading an asset to a specific account ensures that generation with that asset will occur under the same account.

https://api.useapi.net/v1/runwayml/gen4/act-two-voice

Request Headers

Authorization: Bearer {API token}
Content-Type: application/json
# Alternatively you can use multipart/form-data
# Content-Type: multipart/form-data

API token is required, see Setup useapi.net for details.

Request Body

{
    "video_assetId": "Required assetId of the video asset (3-30 seconds) for voice swap",
    "voiceId": "Required voice ID from available voices",
    "exploreMode": true,
    "replyUrl": "Place your call back URL here",
    "replyRef": "Place your reference id here",
    "maxJobs": 5
}

video_assetId is required. Specify the video asset (3-30 seconds duration) you want to apply voice swap to. Use GET /assets/?mediaType=video to see the list of video assets. To upload a new video asset use POST /assets.
voiceId is required. Specify the voice ID to use for voice swap. Use GET /lipsync/voices to see the list of available voices.
exploreMode is optional. Set to true if you have a Runway Unlimited plan and wish to execute relaxed generation. You are not charged credits for Explore mode generations.
replyUrl is optional, if not provided value from useapi.net account will be used.
Place here your callback URL. API will call the provided replyUrl once Runway task completed or failed.
Maximum length 1024 characters.
We recommend using sites like webhook.site to test callback URL functionality.
replyRef is optional, place here your reference id which will be stored and returned along with this Runway task response / result.
Maximum length 1024 characters.
maxJobs is optional, if not provided value for referenced by video assetId account will be used.
Valid range: 1…10.
Runway has dynamic query capacity and guarantees that, for a given account, at least one job will run — often two, and very rarely, three. If you have a single account linked, keep adding new jobs until you receive a 429 response. Once you get a 429, wait for xx seconds or until at least one job completes, then try again. If you need to run more jobs in parallel, simply add more Runway accounts.

Responses

200 OK

Use returned taskId to retrieve task status and results using GET /tasks/taskId. The generated video url can be found in the artifacts array of the task with the status SUCCEEDED.

If you specify the optional parameter replyUrl the API will call the provided replyUrl with task progress updates until the task is complete or fails.

{
  "task": {
    "id": "<uuid>",
    "name": "<voice_name>_<video_name>",
    "image": null,
    "createdAt": "2025-09-08T06:52:26.378Z",
    "updatedAt": "2025-09-08T06:52:26.468Z",
    "taskType": "workflow_s2s_video",
    "options": {
        "name": "<voice_name>_<video_name>",
        "video": "<video url>",
        "voiceId": "<voice id>",
        "seconds": 15,
        "exploreMode": false,
        "assetGroupId": "<uuid>"
    },  
    "status": "PENDING",
    "error": null,
    "progressText": null,
    "progressRatio": "0",
    "estimatedTimeToStartSeconds": 0,
    "artifacts": [],
    "sharedAsset": null,
    "sourceAssetId": null,
    "taskId": "user:user_id-runwayml:account_email-task:task_uuid",
    "code": 200
  }
}

400 Bad Request

{
  "error": "<Error message>",
  "code": 400
}

401 Unauthorized

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

404 Not Found

{
    "error": "Unable to retrieve assetId <uuid> (Not found.)",
    "code": 404
}

412 Insufficient credits

You do not have enough credits to run this task.

{
    "error": "You do not have enough credits to run this task."
}

429 Too Many Requests

Wait in a loop for at least 10..30 seconds and retry again.

There are two possible cases for API response 429:

API query is full and can not accept new gen4/act-two-voice requests. Size of query defined by maxJobs optional parameter.

{
    "error": "Account <Runway account email> is busy executing <Account maxJobs> tasks",
    "runningTasks": {
        "<Runway account email>": [
            {
                "email": "<Runway account email>",
                "taskId": "user:user_id-runwayml:account_email-task:task_#1_uuid",
                "id": "<uuid>",
                "replyUrl": "<replyUrl if provided>",
                "replyRef": "<replyRef if provided>"
            },
            {
                "email": "<Runway account email>",
                "taskId": "user:user_id-runwayml:account_email-task:task_#N_uuid",
                "id": "<uuid>",
                "replyUrl": "<replyUrl if provided>",
                "replyRef": "<replyRef if provided>"
            }
        ]
    },
    "code": 429
}

The API received an HTTP response status 429 from Runway. Runway has dynamic query management and may limit the number of simultaneously executed tasks based on internal service load and policies.

{
    "error": "You have too many tasks running or pending. Please wait for some of them to finish before starting more."
}

Model

{ // TypeScript, all fields are optional
  task: {
    taskId: string
    id: string
    name: string
    image: any
    createdAt: string
    updatedAt: string
    taskType: string
    options: {
        name: string
        video: string
        voiceId: string
        seconds: number
        exploreMode: boolean
        assetGroupId: string
    }
    status: string
    progressText: any
    progressRatio: string
    estimatedTimeToStartSeconds: number
    artifacts: any[]
    sharedAsset: any
    sourceAssetId: any
    error: {
      errorMessage: string
      reason: string
      message: string
      moderation_category: string
      tally_asimov: boolean
    }
    code: number
  }
}

Examples

curl -H "Accept: application/json" \
     -H "Content-Type: application/json" \
     -H "Authorization: Bearer …" \
     -X POST "https://api.useapi.net/v1/runwayml/gen4/act-two-voice" \
     -d '{"video_assetId": "…", "voiceId": "…"}'

const video_assetId = "video asset (3-30 seconds) for voice swap";      
const voiceId = "voice ID from available voices";      
const apiUrl = `https://api.useapi.net/v1/runwayml/gen4/act-two-voice`; 
const token = "API token";
const data = { 
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${token}`,
    'Content-Type': 'application/json' }
};
data.body = JSON.stringify({ 
  video_assetId, voiceId
});
const response = await fetch(apiUrl, data);
const result = await response.json();
console.log("response", {response, result});

import requests
video_assetId = "video asset (3-30 seconds) for voice swap"
voiceId = "voice ID from available voices"
apiUrl = f"https://api.useapi.net/v1/runwayml/gen4/act-two-voice" 
token = "API token"
headers = {
    "Content-Type": "application/json", 
    "Authorization" : f"Bearer {token}"
}
body = {
    "video_assetId": f"{video_assetId}",
    "voiceId": f"{voiceId}"
}
response = requests.post(apiUrl, headers=headers, json=body)
print(response, response.json())