Seedance 2.5 Image to Video API

POST Base URL: https://api.hiapi.ai /v1/tasks

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Image, video, and audio models are called through theUnified Async API POST /v1/tasks endpoint; only the input fields differ (see input parameters below).

Model summary

Model	seedance-2.5/image-to-video
Capability	First-frame / first-last-frame image-to-video
Resolution	720p / 1080p
Duration	4-30 seconds

Generate up to 30 seconds from a first frame or a first/last-frame pair, with the output ratio following the first frame and optional synchronized audio.

Production guidance

Calling the API

• When providing last_frame_url, also provide first_frame_url.
• Use callback.url for task success or failure notifications; read the task object from data in query responses and directly from the callback body.
• Artifact URLs expire; copy files you need to keep into persistent storage.

Best suited for

Animate a still

Add natural motion and camera movement to a poster, product image, illustration, or scene.

first_frame_url

Controlled transitions

Specify both endpoints to create a coherent transition between two images.

first_frame_urllast_frame_url

Sound-on video

Generate synchronized dialogue, effects, and background music for an image-driven shot.

generate_audio

Request parameters

</> Generate example code

model string required

Model ID.

example seedance-2.5/image-to-video

input object required

First-frame and first/last-frame image-to-video parameters.

prompt string required

Motion, camera, scene, and audio instructions. Eleven prompt languages are supported.

first_frame_url string optional

First-frame HTTP(S) URL, data URL, or asset://<id> asset ID. First-frame or first/last-frame input cannot be combined with reference images or audio.

last_frame_url string optional

Last-frame image URL used with first_frame_url. If its ratio differs from the first frame, it is center-cropped. First/last-frame input cannot be combined with reference images or audio.

reference_image_urls string[] optional

Array of up to 30 reference image URLs for subject, style, or composition guidance. Reference images cannot be combined with first_frame_url or last_frame_url.

reference_audio_urls string[] optional

Array of up to 10 reference audio clips for voice or sound guidance. Reference audio cannot be combined with first_frame_url or last_frame_url.

resolution enum optional

Output video resolution.

default 720p enum: 720p1080p

duration integer optional

Output duration in seconds. Accepts integers from 4 to 30.

default 5

aspect_ratio enum optional

Output aspect ratio, derived from the first frame.

default adaptive enum: adaptive

generate_audio boolean optional

Generate synchronized dialogue, effects, and background audio.

default true

output_format enum optional

Output format. mp4 has broad compatibility; mov is intended for professional post-production.

default mp4 enum: mp4mov

watermark boolean optional

Add an AI-generated watermark to the bottom-right corner.

default false

web_search boolean optional

Allow the model to search for current information mentioned in the prompt.

default false

callback object optional

Sends a notification when the task succeeds or fails; read the task object from data in query responses and directly from the callback body.

url string required

HTTPS URL that receives task success or failure notifications.

example https://your-domain.com/hiapi/callback

when enum optional

Triggers when the task succeeds or fails.

default final enum: final

Input requirements

• First-frame/first-last-frame input cannot be combined with reference images or reference audio.
• Input images support jpeg, png, webp, bmp, tiff, and gif; each must be under 30 MB, have sides from 300 to 6000 px, and an aspect ratio from 0.4 to 2.5. SVG, HEIC, and HEIF are not supported. Up to 30 reference images are accepted; total image size must not exceed 120 MB; GIF uses only its first frame.
• Reference audio supports wav and mp3; pass up to 10 clips, each 2-30 seconds and under 15 MB, with a combined limit of 30 seconds.
• aspect_ratio=adaptive means the output video ratio follows the first frame.

Example requests

First-frame generation

Pass only the first frame and let the model create motion.

Request body⧉

{
  "model": "seedance-2.5/image-to-video",
  "input": {
    "prompt": "Move from a static view into a slow orbit",
    "first_frame_url": "https://example.com/first-frame.jpg",
    "resolution": "720p",
    "duration": 6,
    "aspect_ratio": "adaptive"
  }
}

First/last-frame transition

Generate a coherent transition between two images.

Request body⧉

{
  "model": "seedance-2.5/image-to-video",
  "input": {
    "prompt": "A natural time-lapse transition from day to night",
    "first_frame_url": "https://example.com/day.jpg",
    "last_frame_url": "https://example.com/night.jpg",
    "resolution": "720p",
    "duration": 8,
    "aspect_ratio": "adaptive",
    "generate_audio": false
  }
}

Getting the result

1. Read data.taskId from the create-task response.
2. Wait for the callback or query GET /v1/tasks/:id; polling puts the task under data.
3. When status=success, read the video URL from output type=video; a callback reads output directly.

FAQ

Where do I read the task from callback and polling responses?

Read the task object from data in query responses and directly from the callback body.

Can I pass only first_frame_url?

Yes. last_frame_url is optional; without it, the model creates the rest of the shot from the first frame.

What is the difference between image aspect ratio and aspect_ratio?

Input images must have an aspect ratio from 0.4 to 2.5; aspect_ratio=adaptive means the output video ratio follows the first frame.

Can I send first/last frames together with reference images or audio?

No. First-frame/first-last-frame input cannot be combined with reference images or reference audio. First-frame and first/last-frame mode can still set generate_audio=true to generate sound synchronized with the picture.

Next steps

• Install the Seedance 2.5 Skill
• Text to video
• Multimodal reference to video