Seedance 2 API

ReachAPI exposes the Seedance 2 family through the public model IDs seedance-2 and seedance-2-fast.

This page describes how to call Seedance 2 models on ReachAPI, including request fields, constraints, and examples.

Important:

Create task: POST /v1/vids/create
Query task: GET /v1/tasks/{task_id}
Model IDs: seedance-2, seedance-2-fast
Execution mode: asynchronous task
All requests must now send explicit input.content

1. API Overview

HTTP method: POST
Request path: /v1/vids/create
Content-Type: application/json
Result delivery:
- The submission response returns task acceptance information
- The final result is obtained by polling /v1/tasks/{task_id} or by callback_url

2. Authentication and Headers

Example headers:

Authorization: Bearer YOUR_REACH_API_KEY
Content-Type: application/json

3. Model Capability Summary

Model	Duration	Resolution	Aspect ratio	`input.content`	Notes
`seedance-2`	`4-15s`	`480p`, `720p`, `1080p`	`21:9`, `16:9`, `4:3`, `1:1`, `3:4`, `9:16`, `adaptive`	Required	Supports text, image, video, audio reference, editing, and extension
`seedance-2-fast`	`4-15s`	`480p`, `720p`	`21:9`, `16:9`, `4:3`, `1:1`, `3:4`, `9:16`, `adaptive`	Required	Same fields as `seedance-2`, but `1080p` is not currently supported

Notes:

duration_seconds = -1 is supported and allows the model to choose the duration automatically

Seedance video tasks are billed by returned token usage, not by video seconds. Estimated price = token unit price × token consumption. The final bill uses usage.output_tokens in the ReachAPI task response, mapped from BytePlus usage.completion_tokens.

Model	Video input	Resolution	Token price
`seedance-2`	No	480p / 720p	$7.00 / 1M tokens
`seedance-2`	No	1080p	$7.70 / 1M tokens
`seedance-2`	Yes	480p / 720p	$4.30 / 1M tokens
`seedance-2`	Yes	1080p	$4.70 / 1M tokens
`seedance-2-fast`	No	480p / 720p	$5.60 / 1M tokens
`seedance-2-fast`	Yes	480p / 720p	$3.30 / 1M tokens
`seedance-2-fast`	Any	1080p	Not supported

4. Create Task

Request body example:

{
  "model": "seedance-2",
  "callback_url": "https://your-domain.com/callback",
  "input": {
    "content": [
      {
        "type": "text",
        "text": "A cinematic drone shot passing over a coastline at sunrise"
      }
    ],
    "duration_seconds": 6,
    "resolution": "720p",
    "aspect_ratio": "16:9"
  }
}

4.1 Top-Level Parameters

Field	Type	Required	Description
`model`	string	Yes	Must be `seedance-2` or `seedance-2-fast`
`callback_url`	string	No	HTTPS callback URL for terminal task states. Maximum length `2048`. Localhost, local network, and private network targets are rejected
`input`	object	Yes	Video generation parameters

4.2 `input` Parameters

Field	Type	Required	Description
`content`	`array<object>`	Yes	Explicit multimodal input. Must be a non-empty array
`duration_seconds`	integer	No	Output duration. Use `4-15` or `-1` for automatic duration selection
`resolution`	string	Yes	Output resolution. `seedance-2`: `480p`, `720p`, `1080p`; `seedance-2-fast`: `480p`, `720p`
`aspect_ratio`	string	No	Output aspect ratio. Supported values: `21:9`, `16:9`, `4:3`, `1:1`, `3:4`, `9:16`, `adaptive`
`generate_audio`	boolean	No	Requests generated audio
`seed`	integer	No	Random seed. Supported range: `-1` to `4294967295`. Use `-1` for a random result
`safety_identifier`	string	No	End-user safety identifier. Must be an ASCII string up to 64 characters
`watermark`	boolean	No	Passes watermark preference to the underlying model
`return_last_frame`	boolean	No	Requests the last frame image
`edit_mode`	string	No	Controls edit behavior in supported scenarios
`extend_mode`	string	No	Controls extension behavior in supported scenarios

5. `input.content` Structure

Supported type values:

text
image_url
video_url
audio_url

Supported role values:

first_frame
last_frame
reference_image
reference_video
reference_audio

Field details:

Field	Type	Required	Description
`content[].type`	string	Yes	Must be `text`, `image_url`, `video_url`, or `audio_url`
`content[].role`	string	No	If provided, it must be one of the supported roles above. Non-text items should usually provide a role explicitly
`content[].text`	string	Required for `type = text`	Text prompt
`content[].image_url.url`	string	Required for `type = image_url`	Image URL or uploaded asset ID
`content[].video_url.url`	string	Required for `type = video_url`	Video URL or uploaded asset ID. Video Base64 is not currently supported
`content[].audio_url.url`	string	Required for `type = audio_url`	Audio URL or uploaded asset ID

Content constraints:

content must contain at least 1 item
Maximum 9 images
Maximum 3 videos
Maximum 3 audio files
text and audio can appear together only when at least one reference_image or reference_video is also present
Audio-only input is not supported
text + audio by itself is not supported
first_frame / last_frame cannot be mixed with reference_image / reference_video / reference_audio in the same request

Supported Seedance 2 input combinations:

text
optional text + image_url
optional text + video_url
optional text + image_url + audio_url
optional text + image_url + video_url
optional text + video_url + audio_url
optional text + image_url + video_url + audio_url

6. Legacy Fields No Longer Supported

The following fields now return 400:

input.prompt
input.image_url
input.image_urls
input.last_image_url
input.video_urls
input.audio_urls
input.negative_prompt
input.parameters
input.instances
input.service_tier
input.execution_expires_after
input.frames
input.camera_fixed
input.draft
input.content[].draft_task
Any undocumented custom fields

7. Request Examples

7.1 Text-to-Video

curl -X POST "https://direct.reachapi.ai/v1/vids/create" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "seedance-2",
    "input": {
      "content": [
        {
          "type": "text",
          "text": "A stylized travel film scene with dynamic camera movement"
        }
      ],
      "duration_seconds": 8,
      "resolution": "1080p",
      "aspect_ratio": "adaptive",
      "watermark": false
    }
  }'

7.2 Explicit Multimodal Reference Input

curl -X POST "https://direct.reachapi.ai/v1/vids/create" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "seedance-2",
    "input": {
      "content": [
        {
          "type": "text",
          "text": "A stylized travel film scene with dynamic camera movement"
        },
        {
          "type": "image_url",
          "role": "reference_image",
          "image_url": {
            "url": "https://cdn.example.com/scene-start.png"
          }
        },
        {
          "type": "video_url",
          "role": "reference_video",
          "video_url": {
            "url": "https://cdn.example.com/reference-motion.mp4"
          }
        }
      ],
      "duration_seconds": 8,
      "resolution": "1080p",
      "aspect_ratio": "adaptive",
      "watermark": false
    }
  }'

7.3 Reference Video Extension

curl -X POST "https://direct.reachapi.ai/v1/vids/create" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "seedance-2-fast",
    "input": {
      "content": [
        {
          "type": "text",
          "text": "Extend this clip into a faster action sequence"
        },
        {
          "type": "video_url",
          "role": "reference_video",
          "video_url": {
            "url": "https://cdn.example.com/reference-1.mp4"
          }
        }
      ],
      "duration_seconds": 6,
      "resolution": "480p",
      "aspect_ratio": "16:9",
      "extend_mode": "continue"
    }
  }'

8. Create Task Response

Example response:

{
  "code": 200,
  "msg": "",
  "status": "queued",
  "task_id": "task_xxx",
  "data": []
}

9. Query Task Status

Request example:

curl -X GET "https://direct.reachapi.ai/v1/tasks/task_xxx" \
  -H "Authorization: Bearer YOUR_REACH_API_KEY"

Successful response example:

{
  "code": 200,
  "msg": "",
  "status": "success",
  "task_id": "task_xxx",
  "data": [
    {
      "url": "https://cdn.example.com/generated/video-1.mp4"
    }
  ],
  "usage": {
    "input_tokens": 0,
    "output_tokens": 102960,
    "total_tokens": 102960
  },
  "cost": {
    "spend": 0.12
  }
}