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POST
/
veo-3.1-i2v
/
async
curl --request POST \ --url https://api.modellix.ai/api/v1/google/veo-3.1-i2v/async \ --header 'Authorization: Bearer <token>' \ --header 'Content-Type: application/json' \ --data ' { "prompt": "The character waves and smiles at the camera", "image": "https://example.com/frame.jpg" } '
{
  "code": 0,
  "message": "success",
  "data": {
    "status": "pending",
    "task_id": "task-i2v001",
    "model_id": "google/veo-3.1-i2v",
    "get_result": {
      "method": "GET",
      "url": "https://api.modellix.ai/api/v1/tasks/task-i2v001"
    }
  }
}

Documentation Index

Fetch the complete documentation index at: https://docs.modellix.ai/llms.txt

Use this file to discover all available pages before exploring further.

Authorizations

​
Authorization
string
header
required

API Key authentication. Format: Bearer YOUR_API_KEY.

Body

application/json

Veo 3.1 / Veo 3.1 Fast image-to-video request. Two input modes: image mode or referenceImages-only mode, mutually exclusive. Resolution up to 4K. Constraints verified 2026-04-29 against Google raw API, see each parameter for details.

​
prompt
string
required

Video description text guiding the animation

Minimum string length: 1
Example:

"The character waves and smiles at the camera"

​
image
string
required

Starting frame. Accepts an image URL (e.g. https://example.com/frame.jpg). Required unless using referenceImages-only mode. Cannot be combined with referenceImages.

Example:

"https://example.com/frame.jpg"

​
lastFrame
string

End frame. Accepts an image URL. Constraints: Requires image (cannot be used alone). Cannot be combined with referenceImages. durationSeconds must be 8 when using this parameter.

Example:

"https://example.com/last-frame.jpg"

​
negativePrompt
string

Text describing what to avoid in the generated video. Important: Only supported when using image mode. NOT supported when using referenceImages mode — Google will return 400 error "Negative prompt is not supported in your use case".

Example:

"blurry, low quality, distorted"

​
referenceImages
string[]

Reference images for style/character/visual guidance (up to 3). Each item is an image URL (e.g. https://example.com/ref.jpg). Supported only by Veo 3.1 and Veo 3.1 Fast I2V. Can be used without image (referenceImages-only mode). Constraints: Cannot be combined with image or lastFrame. Cannot be combined with negativePrompt. durationSeconds must be 8 when using this parameter.

Maximum array length: 3
Example:
["https://example.com/ref.jpg"]
​
aspectRatio
enum<string>
default:16:9

Video aspect ratio

Available options:
16:9,
9:16
Example:

"16:9"

​
durationSeconds
enum<string>

Video duration in seconds (string type). Constraint: When using lastFrame or referenceImages, must be 8 — values 4 or 6 will be rejected by Google. When not using these features, 4, 6, 8 are all valid.

Available options:
4,
6,
8
Example:

"8"

​
resolution
enum<string>

Video resolution. Constraint: 1080p and 4k are only available when durationSeconds is 8.

Available options:
720p,
1080p,
4k
Example:

"1080p"

​
personGeneration
enum<string>

Person generation policy

Available options:
allow_adult
Example:

"allow_adult"

Response

Task submitted successfully

​
code
integer
required

Response code, 0 indicates success

Example:

0

​
message
string
required

Response message

Example:

"success"

​
data
object
required

Detailed data about the submitted asynchronous task.