Seedance 2.5

{BASE_URL} is https://api.uniall.ai throughout this page.

Updated: 2026-08-12

Overview

UniAll exposes Seedance 2.5 through one stable public model ID: seedance2.5. It supports text-to-video, first-frame and first-and-last-frame generation, multimodal references, video editing, video extension, reusable asset:// media, and optional web search.

Capability	Required input	Key rule
Text-to-video	Prompt	Set `resolution` and `duration`.
First-frame video	One first-frame image	Omit `aspect_ratio` or use `auto`.
First-and-last-frame video	One first-frame and one last-frame image	Omit `aspect_ratio` or use `auto`.
Multimodal reference	Images, videos, or audio	Text is optional; audio-only reference requests are allowed.
Video editing	Prompt and one video	Set `operation: "edit_video"` and `duration: "auto"`.
Video extension	Prompt and one video	Set `operation: "extend_video"` explicitly.

Endpoints And Authentication

Action	Method	Path
Create task	`POST`	`/v1/videos`
Query task	`GET`	`/v1/videos/{task_id}`
Download completed video	`GET`	`/v1/videos/{task_id}/content`

Compatible creation and query aliases remain available to existing clients:

POST /v1/videos/generations
POST /v1/video/generations
GET  /v1/videos/generations/{task_id}
GET  /v1/video/generations/{task_id}

New integrations should use /v1/videos and /v1/videos/{task_id}.

Authorization: Bearer sk-***
Content-Type: application/json

Request Parameters

Parameter	Type	Required	Description
`model`	string	Yes	Must be `seedance2.5`.
`resolution`	string	Yes	`480p` or `720p`.
`size`	string	No	Compatibility alias for `resolution`. If both are present, they must match.
`duration`	integer/string	Yes	Integer from `4` through `30`, or `auto`. Operation-specific rules apply.
`prompt`	string	Conditional	Text instruction. Required for text generation, editing, and extension; optional for media-only reference requests.
`aspect_ratio`	string	No	`auto`, `21:9`, `16:9`, `4:3`, `1:1`, `3:4`, or `9:16`.
`ratio`	string	No	Compatibility alias for `aspect_ratio`; `adaptive` is normalized to `auto`.
`output_format`	string	No	`mp4` or `mov`; default `mp4`. Compatible clients may use `extra_body.output_format`.
`content`	object[]	No	Multimodal image, video, and audio items with explicit roles.
`operation`	string	Conditional	Explicitly required for `edit_video` and `extend_video`; use `reference_to_video` for multimodal reference generation when an operation is sent.
`generate_audio`	boolean	No	Whether the task should generate audio.
`seed`	integer	No	Random seed for reproducible variation where supported.
`watermark`	boolean	No	Whether to add a watermark.
`return_last_frame`	boolean	No	Whether to return the final generated frame when available.
`tools`	object[]	No	Only `[{"type":"web_search"}]` is accepted.

The following fields are not part of the public Seedance 2.5 contract and are rejected: draft, frames, camera_fixed, and service_tier: "flex".

Minimal Text-To-Video Request

curl -X POST "{BASE_URL}/v1/videos" \
  -H "Authorization: Bearer sk-***" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "seedance2.5",
    "prompt": "A cinematic city street after rain",
    "resolution": "720p",
    "duration": 8,
    "aspect_ratio": "16:9",
    "output_format": "mp4"
  }'

Media Inputs

Use content[] for new multimodal integrations. Each item carries one media type and an explicit role.

Item type	URL field	Supported roles
`image_url`	`image_url.url`	`first_frame`, `last_frame`, `reference_image`
`video_url`	`video_url.url`	`reference_video`
`audio_url`	`audio_url.url`	`reference_audio`

Media URLs may be public HTTP(S) URLs or valid asset:// references. HTTP(S) media must remain reachable by the UniAll service without cookies or custom request headers. See the Seedance Material Library for creating reusable asset:// inputs.

The compatibility fields image, images, video, videos, audios, and last_image remain accepted. Do not send conflicting values through both content[] and compatibility fields.

Media Limits

Up to 30 images.
Up to 10 videos.
Up to 10 audio files.
Up to 50 media items in total.
A multimodal request may omit text.
An audio-only reference request is valid.

Operation Rules

Mode	`operation`	`duration`	`aspect_ratio`
Text-to-video	Omit	`auto` or integer `4..30`	Any supported value
First-frame video	Omit	`auto` or integer `4..30`	Omit or `auto`
First-and-last-frame video	Omit	`auto` or integer `4..30`	Omit or `auto`
Multimodal reference	`reference_to_video` when specified	`auto` or integer `4..30`	Follow the media mode; frame inputs require `auto`
Video editing	`edit_video` required	`auto` only	Omit or `auto`
Video extension	`extend_video` required	`auto` or integer `4..30`	Omit or `auto`

Do not rely on prompt keywords to select editing or extension. Those requests must carry an explicit operation.

Request Examples

First-And-Last-Frame Video

{
  "model": "seedance2.5",
  "prompt": "Move naturally from the first composition to the last while preserving the subject.",
  "resolution": "720p",
  "duration": 10,
  "aspect_ratio": "auto",
  "content": [
    {
      "type": "image_url",
      "image_url": {
        "url": "https://example.com/first.png"
      },
      "role": "first_frame"
    },
    {
      "type": "image_url",
      "image_url": {
        "url": "https://example.com/last.png"
      },
      "role": "last_frame"
    }
  ]
}

For a single first frame, send only the first_frame item. In both frame modes, fixed aspect ratios are rejected because the source frame determines the composition.

Multimodal Reference

{
  "model": "seedance2.5",
  "operation": "reference_to_video",
  "resolution": "720p",
  "duration": 12,
  "content": [
    {
      "type": "image_url",
      "image_url": {
        "url": "https://example.com/product.png"
      },
      "role": "reference_image"
    },
    {
      "type": "video_url",
      "video_url": {
        "url": "https://example.com/motion.mp4"
      },
      "role": "reference_video"
    },
    {
      "type": "audio_url",
      "audio_url": {
        "url": "https://example.com/music.mp3"
      },
      "role": "reference_audio"
    }
  ]
}

Video Editing

{
  "model": "seedance2.5",
  "prompt": "Replace the sky and preserve the subject",
  "video": "https://example.com/source.mp4",
  "operation": "edit_video",
  "resolution": "720p",
  "duration": "auto",
  "aspect_ratio": "auto"
}

Video Extension

{
  "model": "seedance2.5",
  "prompt": "Continue the camera movement into the illuminated square.",
  "video": "asset://mat_xxxxxxxxxxxxx",
  "operation": "extend_video",
  "resolution": "720p",
  "duration": 8,
  "aspect_ratio": "auto",
  "output_format": "mov"
}

Web Search

{
  "model": "seedance2.5",
  "prompt": "Create a concise visual recap of the latest public spaceflight milestone.",
  "resolution": "720p",
  "duration": 8,
  "tools": [
    {
      "type": "web_search"
    }
  ]
}

Web search can be combined with media inputs. No other tools shape is accepted.

Create Response And Task Lifecycle

{
  "id": "task_xxxxxxxxxxxxx",
  "task_id": "task_xxxxxxxxxxxxx",
  "object": "video.generation.job",
  "model": "seedance2.5",
  "status": "queued",
  "progress": 0,
  "created_at": 1786492800
}

Store the public id or task_id. Poll GET /v1/videos/{task_id} every 2 to 5 seconds and stop when status is completed or failed. A completed task returns a public result URL; you can also retrieve the file through the authenticated /v1/videos/{task_id}/content endpoint.

See Video Generation Overview for public status fields, completed and failed response examples, and download handling. Client applications should use only the public task ID, status, result, usage, and error fields documented by UniAll.

Billing Notes

Seedance 2.5 is settled by valid completion Token usage after the task finishes. Any pre-deduction is an estimate; use the completed task's effective usage and settlement record as the final amount.

Input type	Reference base rate per 1 million completion Tokens
Request without video input	About `$10.294117647` (`70 CNY / 6.8`)
Request containing video input	About `$6.176470588` (`42 CNY / 6.8`)

480p and 720p use the same Token unit rate.
These values are completion-Token reference rates, not fixed per-second prices.
Account and pricing-group rules can change the final user price. Use the current UniAll pricing page and task settlement record as the authoritative source.

Common Errors

Error	Cause	Fix
Missing parameter	`resolution` or `duration` is absent	Send both required fields.
Invalid resolution	`1080p`, `4k`, or another unsupported value was sent	Use `480p` or `720p`.
Conflicting aliases	`resolution` and `size` contain different values	Remove `size` or make the values identical.
Invalid edit duration	`edit_video` uses an integer duration	Set `duration` to `auto`.
Invalid aspect ratio	A frame, edit, or extension request uses a fixed ratio	Omit `aspect_ratio` or set it to `auto`.
Media limit exceeded	Per-type or total media limits were exceeded	Reduce media to the documented limits.
Media unavailable	A URL is private, expired, or unreachable from the public internet	Use a stable public URL or an available `asset://` material.
Invalid tools	`tools` is not exactly the supported web-search structure	Send `[{"type":"web_search"}]` or omit `tools`.
Unsupported field	`draft`, `frames`, `camera_fixed`, or `service_tier: "flex"` was sent	Remove the unsupported field.

Overview​

Endpoints And Authentication​

Request Parameters​

Minimal Text-To-Video Request​

Media Inputs​

Media Limits​

Operation Rules​

Request Examples​

First-And-Last-Frame Video​

Multimodal Reference​

Video Editing​

Video Extension​

Web Search​

Create Response And Task Lifecycle​

Billing Notes​

Common Errors​

Related Pages​