> ## Documentation Index
> Fetch the complete documentation index at: https://docs.unifically.com/llms.txt
> Use this file to discover all available pages before exploring further.

# SeeDance 2.5 Flash

> Faster, lower-cost SeeDance 2.5 video generation with native audio, references, frame workflows, parameters, responses, and API examples.

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

Try it in the browser: [SeeDance 2.5 Flash API playground](https://unifically.com/models/seedance-2.5-flash).

> [!TIP]
>
> Need 1080p or more reference assets per request? Use [SeeDance 2.5](https://docs.unifically.com/models/video/bytedance/seedance-2.5.md), which takes the same request fields.

## Model

```
bytedance/seedance-2.5-flash
```

## 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 10 reference image URLs. Reference them as `[Image1]`, `[Image2]`, and so on |
| `video_urls` | string\[] | No | `null` | Up to 5 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 5 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 |
| `nsfw_check` | boolean | No | `false` | Check the prompt and input images for NSFW content before generating. Off unless set to `true` |

The total number of reference assets across images, videos, and audio cannot exceed 20. First/last frame URLs cannot be combined with `image_urls`, `video_urls`, or `audio_urls`.

Reference videos are billed by length: every second of reference video counts like a second of output. Reference images and audio add nothing to the price.

## Example - Text-to-Video

```bash theme={null}
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-flash",
    "input": {
      "prompt": "A red kite dancing over a green hill on a sunny afternoon, wind rustling through the grass",
      "aspect_ratio": "16:9",
      "duration": 8,
      "resolution": "720p",
      "generate_audio": true
    }
  }'
```

## Example - First & Last Frame

```bash theme={null}
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-flash",
    "input": {
      "prompt": "The camera glides forward as the morning fog lifts off the lake",
      "duration": 6,
      "resolution": "720p",
      "first_frame_url": "https://example.com/start.jpg",
      "last_frame_url": "https://example.com/end.jpg"
    }
  }'
```

## Example - Image and Video References

```bash theme={null}
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-flash",
    "input": {
      "prompt": "The character from [Image1] walks through the scene, following the camera movement in [Video1]",
      "duration": 5,
      "resolution": "480p",
      "image_urls": [
        "https://example.com/character.jpg"
      ],
      "video_urls": [
        "https://example.com/camera-reference.mp4"
      ]
    }
  }'
```

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

```json theme={null}
{
  "code": 200,
  "success": true,
  "data": {
    "task_id": "abc123def456",
    "status": "processing"
  }
}
```

> [!NOTE]
>
> **Volume discounts** are available for almost all models. Reach out at [contact@unifically.com](mailto:contact@unifically.com) to discuss custom pricing.


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