SeeDance 2.5 - Unifically

Generate videos using ByteDance SeeDance 2.5 with text-to-video, first/last frame, and multimodal reference workflows. It supports image, video, and audio references, synchronized native audio, 4–30 second durations, and 480p or 720p output.

Model

bytedance/seedance-2.5

Unifically automatically routes prompt-only requests through the text generation channel and requests containing any reference media through the multimodal channel. No routing option is required in your request.

Request types

Request type	Required inputs	Optional inputs	Notes
Text-to-video	`prompt`	`aspect_ratio`, `duration`, `resolution`, `generate_audio`, `seed`	Do not include reference media URLs
First/last frame	`first_frame_url`, `last_frame_url`	`prompt`, `duration`, `resolution`, `generate_audio`, `seed`	Both frame URLs are required. `aspect_ratio` must be `adaptive` because the output follows the first frame
Multimodal reference	`prompt`, at least one reference URL	`image_urls`, `video_urls`, `audio_urls`, `aspect_ratio`, `duration`, `resolution`, `generate_audio`, `seed`	Reference assets in the prompt as `[Image1]`, `[Video1]`, and `[Audio1]`

Parameters

Parameter	Type	Required	Default	Description
`prompt`	string	Conditional	`""`	Creative description (max 5,000 characters). Required for text-to-video and multimodal reference requests; optional for first/last frame requests. Reference media in array order using `[Image1]`, `[Video1]`, or `[Audio1]`
`resolution`	string	No	`"480p"`	`480p` or `720p`
`duration`	integer	No	`4`	Output duration in whole seconds (4–30)
`aspect_ratio`	string	No	`"adaptive"`	`adaptive`, `1:1`, `3:4`, `4:3`, `9:16`, `16:9`, or `21:9`. Must be `adaptive` for first/last frame requests
`generate_audio`	boolean	No	`true`	Generate synchronized voice, sound effects, and background music with the video
`seed`	integer	No	Random	Seed from `-1` to `2147483647`. Use the same numeric seed for reproducible results; `-1` selects a random seed
`first_frame_url`	string	Conditional	`null`	First frame image URL. Must be provided together with `last_frame_url` and cannot be combined with reference arrays
`last_frame_url`	string	Conditional	`null`	Last frame image URL. Must be provided together with `first_frame_url` and cannot be combined with reference arrays
`image_urls`	string[]	No	`null`	Up to 30 reference image URLs. Reference them as `[Image1]`, `[Image2]`, and so on
`video_urls`	string[]	No	`null`	Up to 10 reference video URLs with a combined duration of up to 30 seconds. Each video must contain at least 409,600 pixels. Reference them as `[Video1]`, `[Video2]`, and so on
`audio_urls`	string[]	No	`null`	Up to 10 reference audio URLs with a combined duration of up to 30 seconds. Audio-only reference requests are supported. Reference them as `[Audio1]`, `[Audio2]`, and so on

The total number of reference assets across images, videos, and audio cannot exceed 50. First/last frame URLs cannot be combined with image_urls, video_urls, or audio_urls.

Example - Text-to-Video

curl -X POST https://api.unifically.com/v1/tasks \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "bytedance/seedance-2.5",
    "input": {
      "prompt": "A cinematic tracking shot through a bustling night market in the rain, with natural crowd ambience and distant music",
      "aspect_ratio": "16:9",
      "duration": 12,
      "resolution": "720p",
      "generate_audio": true
    }
  }'

Example - First & Last Frame

curl -X POST https://api.unifically.com/v1/tasks \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "bytedance/seedance-2.5",
    "input": {
      "prompt": "The camera glides forward as sunrise gradually illuminates the valley",
      "duration": 10,
      "resolution": "720p",
      "first_frame_url": "https://example.com/start.jpg",
      "last_frame_url": "https://example.com/end.jpg"
    }
  }'

Example - Video and Audio References

curl -X POST https://api.unifically.com/v1/tasks \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "bytedance/seedance-2.5",
    "input": {
      "prompt": "Create a new cinematic sequence inspired by the camera movement in [Video1] and timed to the rhythm of [Audio1]",
      "duration": 15,
      "resolution": "720p",
      "video_urls": [
        "https://example.com/camera-reference.mp4"
      ],
      "audio_urls": [
        "https://example.com/music-reference.mp3"
      ]
    }
  }'

References are numbered independently and in array order: the first image is [Image1], the first video is [Video1], and the first audio clip is [Audio1].

Response

{
  "code": 200,
  "success": true,
  "data": {
    "task_id": "abc123def456",
    "status": "processing"
  }
}

⌘I