> ## 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.

# Grok Imagine Video 1.5 Fast

> Generate videos with xAI Grok Imagine Video 1.5 Fast. See supported inputs, parameters, pricing, response fields, and API examples.

Generate AI videos quickly using xAI's Grok Imagine Video 1.5 Fast — a speed-optimized build of Grok Imagine 1.5 Video with text-to-video, image-to-video, multi-image references, saved characters, props, locations, and preset voices.

Try it in the browser: [Grok Imagine API playground](https://unifically.com/models/grok-imagine).

<Warning>
  `xai/grok-imagine-video` is no longer supported. Use `xai/grok-imagine-1.5-fast-video` instead — same model, same parameters, same prices. Requests sent to the old key are rejected.
</Warning>

## Model

```
xai/grok-imagine-1.5-fast-video
```

## Pricing

Billed per second of output video.

| Resolution | Per second |
| - | - |
| 480p | \$0.04 |
| 720p | \$0.07 |
| 1080p | \$0.125 |

## Parameters

| Parameter | Type | Required | Default | Allowed Values | Description |
| - | - | - | - | - | - |
| `prompt` | string | Yes | — | — | Video prompt. Use `@ImageN` for an item in `image_urls`, or `@audio1` for the request-level `voice` |
| `aspect_ratio` | string | No | `"1:1"` | `"1:1"`, `"2:3"`, `"3:2"`, `"9:16"`, `"16:9"` | Output aspect ratio |
| `duration` | int | No | `6` | `1`–`30` | Video duration in seconds |
| `resolution` | string | No | `"720p"` | `"480p"`, `"720p"`, `"1080p"` | Output resolution |
| `start_image_url` | string | No | `null` | — | Start frame image URL. Cannot be combined with `image_urls` or media references |
| `image_urls` | string\[] | No | `null` | 1–7 URLs | Ordered reference images. Cannot be combined with `start_image_url` |
| `character_id` | string | No | `null` | — | ID of an existing saved Grok character reference |
| `character` | object | No | `null` | — | Transient character reference: 3 images, or 2 images plus a preset `voice` |
| `prop` | object | No | `null` | — | Transient prop reference containing a name and 1–3 images |
| `location` | object | No | `null` | — | Transient location reference containing a name and 1–3 images |
| `voice` | string | No | `null` | [Grok voice ID](/api-reference/resources#get-grok-imagine-voices) | Case-insensitive preset voice name. Audio URLs are not accepted |
| `audio` | boolean | No | `true` | `true`, `false` | Generate audio. `false` renders a silent clip |
| `video_preset` | string | No | `"custom"` | `"custom"`, `"spicy"`, `"fun"`, `"normal"` | Generation style preset |
| `nsfw_check` | boolean | No | `true` | `true`, `false` | Check uploaded media inputs for NSFW content |

<Note>
  Audio generation works for both text-to-video and requests with visual references. Set `audio: false` only when you want to suppress generated audio. A preset `voice` still requires a visual input and cannot be combined with `audio: false`.
</Note>

### Media reference objects

| Object | Required fields | Rules |
| - | - | - |
| `character` | `image_urls` | Exactly 3 images without a voice, or exactly 2 images plus one preset `voice`. `name` and `description` are optional |
| `prop` | `name`, `image_urls` | 1–3 images. `description` is optional |
| `location` | `name`, `image_urls` | 1–3 images. `description` is optional |

Transient `character`, `prop`, and `location` references are created for the task and automatically deleted after the generation completes or fails. A caller-provided `character_id` is never deleted.

**Video presets:**

| Preset | Style |
| - | - |
| `custom` | Default generation |
| `spicy` | Extremely spicy/NSFW |
| `fun` | Extremely crazy/fun |
| `normal` | Normal style |

## Example requests

### Text to video

Text-only requests can generate audio. This example disables it explicitly.

```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": "xai/grok-imagine-1.5-fast-video",
    "input": {
      "prompt": "A futuristic cityscape at sunset with flying cars",
      "duration": 10,
      "resolution": "1080p",
      "aspect_ratio": "16:9",
      "audio": false,
      "video_preset": "custom"
    }
  }'
```

### Image to video with generated audio

```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": "xai/grok-imagine-1.5-fast-video",
    "input": {
      "prompt": "Camera slowly zooms in while clouds move across the sky",
      "start_image_url": "https://example.com/landscape.jpg",
      "audio": true,
      "duration": 6,
      "resolution": "720p",
      "aspect_ratio": "16:9"
    }
  }'
```

### Reference images

```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": "xai/grok-imagine-1.5-fast-video",
    "input": {
      "prompt": "The woman in @Image1 walks into the neon-lit bar from @Image2",
      "image_urls": [
        "https://example.com/woman.jpg",
        "https://example.com/neon-bar.jpg"
      ],
      "audio": false,
      "duration": 10,
      "resolution": "720p",
      "aspect_ratio": "16:9"
    }
  }'
```

### Character with a preset voice

```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": "xai/grok-imagine-1.5-fast-video",
    "input": {
      "prompt": "The host looks into the camera and welcomes the audience",
      "character": {
        "name": "Host",
        "description": "A friendly studio presenter",
        "image_urls": [
          "https://example.com/host-front.jpg",
          "https://example.com/host-side.jpg"
        ],
        "voice": "eve"
      },
      "audio": true,
      "duration": 6,
      "resolution": "480p",
      "aspect_ratio": "16:9"
    }
  }'
```

Use `GET /v1/resources/grok/voices` to discover all preset IDs, descriptions, tags, and preview URLs.

## Prompt references

| Token | Refers to |
| - | - |
| `@Image1`, `@Image2`, … | Items from `image_urls`, in the order sent |
| `@audio1` | The request-level preset selected with `voice` |

<Note>
  Prompt reference tokens, `character`, `prop`, `location`, `voice`, and `video_preset` are specific to `xai/grok-imagine-1.5-fast-video`. [Grok Imagine Video 1.5](/models/video/xai/grok-imagine-1.5-video) uses `image_urls`, `end_image_url`, `keyframes`, and `voice_ids` instead.
</Note>

## Extend and upscale

Completed tasks from this model can be passed by `task_id` to [Grok Imagine 1.5 Fast Video Extend](/models/video/xai/grok-imagine-video-extend) (`xai/grok-imagine-video-extend`) and [Grok Imagine Upscale](/models/video/xai/grok-imagine-upscale) (`xai/grok-imagine-upscale`).

## 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.
</Note>


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