---
title: LTX-2.3 Fast | Runware Docs
url: https://runware.ai/docs/models/lightricks-ltx-2-3-fast
description: Fast multimodal video generation optimized for rapid iteration
---
# LTX-2.3 Fast

LTX-2.3 Fast is a performance-optimized variant of LTX 2.3 designed for rapid video generation with synchronized audio. It supports text-to-video, image-to-video, and audio-conditioned workflows while prioritizing speed, responsiveness, and cost efficiency for draft, preview, and high-velocity creative production use cases.

- **ID**: `lightricks:ltx@2.3-fast`
- **Status**: live
- **Creator**: Lightricks
- **Release Date**: March 5, 2026
- **Capabilities**: Text to Video, Image to Video, Audio to Video

## Pricing

- **1920x1080 · 1s**: `$0.06`
- **1080x1920 · 1s**: `$0.06`
- **2560x1440 · 1s**: `$0.12`
- **1440x2560 · 1s**: `$0.12`
- **3840x2160 · 1s**: `$0.24`
- **2160x3840 · 1s**: `$0.24`

## Compatibility & Validation

Either provide `inputs.frameImages`, or specify `width/height`.

---

Parameter constraints vary based on the configuration:

| Dimensions | duration | fps |
| --- | --- | --- |
| `1920x1080` | `6` `8` `10` `12` `14` `16` `18` `20` | `24` `25` |
| `1080x1920` | `6` `8` `10` `12` `14` `16` `18` `20` | `24` `25` |
| `Other` | `6` `8` `10` | `any` |

---

`width` and `height` must be used together.

---

The following dimension combinations are supported:

| Configuration | Dimensions |
| --- | --- |
| `1080p (16:9)` | `1920x1080` |
| `1440p (16:9)` | `2560x1440` |
| `4K (16:9)` | `3840x2160` |
| `1080p (9:16)` | `1080x1920` |
| `1440p (9:16)` | `1440x2560` |
| `4K (9:16)` | `2160x3840` |

## Request Parameters

**API Options**

Platform-level options for task execution and delivery.

### [taskType](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-tasktype)

- **Type**: `string`
- **Required**: true
- **Value**: `videoInference`

Identifier for the type of task being performed

### [taskUUID](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-taskuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task.

### [outputType](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-outputtype)

- **Type**: `string`
- **Default**: `URL`

Video output type.

**Allowed values**: `URL`

### [outputFormat](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-outputformat)

- **Type**: `string`
- **Default**: `MP4`

Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities.

- \`MP4\`: Widely supported video container (H.264), recommended for general use.
- \`WEBM\`: Optimized for web delivery.
- \`MOV\`: QuickTime format, common in professional workflows (Apple ecosystem).

**Allowed values**: `MP4` `WEBM` `MOV`

### [outputQuality](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-outputquality)

- **Type**: `integer`
- **Min**: `20`
- **Max**: `99`
- **Default**: `95`

Compression quality of the output. Higher values preserve quality but increase file size.

### [webhookURL](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-webhookurl)

- **Type**: `string`
- **Format**: `URI`

Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available.

**Learn more** (1 resource):

- [Webhooks](https://runware.ai/docs/platform/webhooks) (platform)

### [deliveryMethod](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-deliverymethod)

- **Type**: `string`
- **Default**: `async`

Determines how the API delivers task results.

**Allowed values**:

- `async` Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse. Required for long-running tasks like video generation.

**Learn more** (1 resource):

- [Task Polling](https://runware.ai/docs/platform/task-polling) (platform)

### [uploadEndpoint](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-uploadendpoint)

- **Type**: `string`
- **Format**: `URI`

Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials.

**Common use cases:**

- **Cloud storage**: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs.
- **CDN integration**: Upload to content delivery networks for immediate distribution.

```text
// S3 presigned URL for secure upload
https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600

// Google Cloud Storage presigned URL
https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789

// Custom storage endpoint
https://storage.example.com/uploads/generated-image.jpg
```

The content data will be sent as the request body to the specified URL when generation is complete.

### [safety](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-safety)

- **Path**: `safety.checkContent`
- **Type**: `object (2 properties)`

Content safety checking configuration for video generation.

#### [checkContent](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-safety-checkcontent)

- **Path**: `safety.checkContent`
- **Type**: `boolean`
- **Default**: `false`

Enable or disable content safety checking. When enabled, defaults to `fast` mode.

#### [mode](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-safety-mode)

- **Path**: `safety.mode`
- **Type**: `string`
- **Default**: `none`

Safety checking mode for video generation.

**Allowed values**:

- `none` Disables checking.
- `fast` Checks key frames.
- `full` Checks all frames.

### [ttl](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-ttl)

- **Type**: `integer`
- **Min**: `60`

Time-to-live (TTL) in seconds for generated content. Only applies when `outputType` is `URL`.

### [includeCost](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-includecost)

- **Type**: `boolean`
- **Default**: `false`

Include task cost in the response.

### [numberResults](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-numberresults)

- **Type**: `integer`
- **Min**: `1`
- **Max**: `4`
- **Default**: `1`

Number of results to generate. Each result uses a different seed, producing variations of the same parameters.

**Inputs**

Input resources for the task (images, audio, etc). These must be nested inside the \`inputs\` object.

### [frameImages](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-inputs-frameimages)

- **Path**: `inputs.frameImages`
- **Type**: `array of strings or objects`

An array of frame-specific image inputs to guide video generation. Each item can be either a plain image input (UUID, URL, Data URI, or Base64) or an object that pairs an image with a target frame position.

The `frameImages` parameter allows you to constrain specific frames within the video sequence, ensuring that particular visual content appears at designated points. This is different from `referenceImages`, which provide overall visual guidance without constraining specific timeline positions.

When the `frame` parameter is omitted, automatic distribution rules apply:

- **1 image**: Used as the first frame.

**Examples**:

**Shorthand format:** When you don't need to specify a frame position, you can pass a plain image input directly.

```json
"frameImages": [
  "aac49721-1964-481a-ae78-8a4e29b91402"
]
```

**Object format:** When you need to specify a frame position, use an object with `image` and `frame`.

```json
"frameImages": [
  {
    "image": "aac49721-1964-481a-ae78-8a4e29b91402",
    "frame": "first"
  }
]
```

**Format 1: string[]**:

- **Type**: `string`

Image input (UUID, URL, Data URI, or Base64).

**Format 2: object[]**:

#### [image](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-inputs-frameimages-format-2-image)

- **Path**: `inputs.frameImages.image`
- **Type**: `string`
- **Required**: true

Image input (UUID, URL, Data URI, or Base64).

#### [frame](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-inputs-frameimages-format-2-frame)

- **Path**: `inputs.frameImages.frame`
- **Type**: `object`

Target frame position for the image. This model only supports the first frame.

**Allowed values**:

- `first` First frame of the video.
- `0` Frame index 0 (first frame).

**Generation Parameters**

Core parameters for controlling the generated content.

### [model](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-model)

- **Type**: `string`
- **Required**: true
- **Value**: `lightricks:ltx@2.3-fast`

Identifier of the model to use for generation.

**Learn more** (3 resources):

- [Text To Image: Model Selection The Foundation Of Generation](https://runware.ai/docs/guides/text-to-image#model-selection-the-foundation-of-generation) (guide)
- [Image Inpainting: Model Specialized Inpainting Models](https://runware.ai/docs/guides/image-inpainting#model-specialized-inpainting-models) (guide)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/guides/image-outpainting#other-critical-parameters) (guide)

### [positivePrompt](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-positiveprompt)

- **Type**: `string`
- **Required**: true
- **Min**: `2`
- **Max**: `10000`

Text prompt describing elements to include in the generated output.

**Learn more** (2 resources):

- [Text To Image: Prompts Guiding The Generation](https://runware.ai/docs/guides/text-to-image#prompts-guiding-the-generation) (guide)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/guides/image-outpainting#other-critical-parameters) (guide)

### [width](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-width)

- **Type**: `integer`
- **Required**: true
- **Paired with**: height

Width of the generated media in pixels.

**Learn more** (2 resources):

- [Image To Image: Dimensions Changing Aspect Ratio](https://runware.ai/docs/guides/image-to-image#dimensions-changing-aspect-ratio) (guide)
- [Image Outpainting: Dimensions Critical For Outpainting](https://runware.ai/docs/guides/image-outpainting#dimensions-critical-for-outpainting) (guide)

### [height](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-height)

- **Type**: `integer`
- **Required**: true
- **Paired with**: width

Height of the generated media in pixels.

**Learn more** (2 resources):

- [Image To Image: Dimensions Changing Aspect Ratio](https://runware.ai/docs/guides/image-to-image#dimensions-changing-aspect-ratio) (guide)
- [Image Outpainting: Dimensions Critical For Outpainting](https://runware.ai/docs/guides/image-outpainting#dimensions-critical-for-outpainting) (guide)

### [duration](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-duration)

- **Type**: `float`
- **Default**: `6`

Length of the generated video in seconds. The total number of frames produced is determined by duration multiplied by the model's frame rate (fps).

### [fps](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-fps)

- **Type**: `integer`
- **Default**: `25`

Frames per second for video generation. Higher values create smoother motion but require more processing time.

**Allowed values**: `24` `25` `48` `50`

**Settings**

Technical parameters to fine-tune the inference process. These must be nested inside the \`settings\` object.

### [audio](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#request-settings-audio)

- **Path**: `settings.audio`
- **Type**: `boolean`
- **Default**: `true`

Generate synchronized audio.

## Response Parameters

### [taskType](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-tasktype)

- **Type**: `string`
- **Required**: true
- **Value**: `videoInference`

Type of the task.

### [taskUUID](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-taskuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID of the task.

### [videoUUID](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-videouuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID of the output video.

### [videoURL](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-videourl)

- **Type**: `string`
- **Format**: `URI`

URL of the output video.

### [videoBase64Data](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-videobase64data)

- **Type**: `string`

Base64-encoded video data.

### [videoDataURI](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-videodatauri)

- **Type**: `string`
- **Format**: `URI`

Data URI of the output video.

### [seed](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-seed)

- **Type**: `integer`

The seed used for generation. If none was provided, shows the randomly generated seed.

### [NSFWContent](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-nsfwcontent)

- **Type**: `boolean`

Flag indicating if NSFW content was detected.

### [cost](https://runware.ai/docs/models/lightricks-ltx-2-3-fast#response-cost)

- **Type**: `float`

Task cost in USD. Present when `includeCost` is set to `true` in the request.

## Examples

### Neon Rain Alley Chase (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-3-fast/80ab15fd-6706-4ef0-a027-3ad582721552.mp4)

**Request**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "44dfa40f-3edc-44d7-9c16-586920b953c4",
  "model": "lightricks:ltx@2.3-fast",
  "positivePrompt": "A cinematic cyberpunk alley at night during heavy rain, glossy neon reflections on wet pavement, a masked courier sprinting through drifting steam while hovering police drones sweep searchlights overhead, dynamic handheld camera movement, parallax depth, flickering holographic shop signs in magenta and cyan, puddle splashes, distant traffic glow, tense atmospheric action, realistic motion, richly detailed environment, synchronized urban chase audio with rain, footsteps, drone hum, echoing sirens, and pulsing synth tension",
  "width": 1920,
  "height": 1080,
  "duration": 6,
  "fps": 25,
  "settings": {
    "audio": true
  }
}
```

**Response**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "44dfa40f-3edc-44d7-9c16-586920b953c4",
  "videoUUID": "c85254e5-89e3-45c0-90e8-ab37bcde5161",
  "videoURL": "https://vm.runware.ai/video/os/a01d21/ws/5/vi/c85254e5-89e3-45c0-90e8-ab37bcde5161.mp4",
  "cost": 0.24
}
```

---

### Cinematic POV Football (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-3-fast/ede8504b-2392-4bb4-b31d-518c5506813c.mp4)

**Request**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "a8196bb5-f009-4929-b013-2bb22d3f9425",
  "model": "lightricks:ltx@2.3-fast",
  "positivePrompt": "First-person cinematic POV of an elite football player sprinting down the field during a night championship match, bright stadium floodlights, roaring crowd, defenders closing in, dynamic head-mounted camera motion, realistic hands and arms pumping, turf flying up under cleats, dramatic near-collision, fast dodge, spinning past a tackle, rushing toward the end zone, broadcast-quality realism, high energy, intense sports cinematography, natural motion blur, synchronized crowd cheers, footsteps, breath, impact sounds, immersive live stadium atmosphere",
  "width": 1920,
  "height": 1080,
  "duration": 6,
  "fps": 25,
  "settings": {
    "audio": true
  }
}
```

**Response**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "a8196bb5-f009-4929-b013-2bb22d3f9425",
  "videoUUID": "fed11704-6d52-49b2-bc49-2af737664456",
  "videoURL": "https://vm.runware.ai/video/os/a09d21/ws/5/vi/fed11704-6d52-49b2-bc49-2af737664456.mp4",
  "cost": 0.24
}
```

---

### Neon Alley Chase (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-3-fast/fa3485d7-5854-4eb2-9f58-9311ea8832dc.mp4)

**Request**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "b99dcaa0-3c5b-4a99-b8c8-92d2740c4434",
  "model": "lightricks:ltx@2.3-fast",
  "positivePrompt": "A cinematic night-time cyberpunk alley soaked in rain, glowing neon signs in magenta and cyan reflecting on wet pavement, a sleek courier on a futuristic electric bike speeding through drifting steam, market tarps fluttering, puddles splashing, holographic billboards flickering overhead, dynamic camera tracking from low angle to side follow shot, rich atmosphere, dramatic motion blur, highly detailed environment, realistic lighting, energetic urban ambience with synchronized sound of rainfall, electric motor whine, distant sirens, buzzing signs, and tires spraying water",
  "width": 1920,
  "height": 1080,
  "duration": 6,
  "fps": 25,
  "settings": {
    "audio": true
  }
}
```

**Response**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "b99dcaa0-3c5b-4a99-b8c8-92d2740c4434",
  "videoUUID": "d5419bed-1a50-4ffb-a27a-e799007ada70",
  "videoURL": "https://vm.runware.ai/video/os/a17d13/ws/5/vi/d5419bed-1a50-4ffb-a27a-e799007ada70.mp4",
  "cost": 0.24
}
```

---

### Cinematic F1 Racing (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-3-fast/02f955e8-70b5-4f89-bba9-ce550d1d0c46.mp4)

**Request**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "f92a00b4-442e-4981-9878-a8bf9bdb2554",
  "model": "lightricks:ltx@2.3-fast",
  "positivePrompt": "A cinematic Formula 1 race at golden hour on a world-class street circuit, low-slung camera tracking inches above the asphalt as sleek red and black F1 cars thunder through a tight corner, tire smoke, heat haze, sparks under the chassis, dramatic overtakes, cheering grandstands, fluttering flags, realistic reflections on polished bodywork, shallow depth of field, broadcast-grade action cinematography, intense speed, dynamic motion blur, crisp detail, realistic lighting, immersive atmosphere",
  "width": 1920,
  "height": 1080,
  "duration": 6,
  "fps": 25,
  "settings": {
    "audio": true
  }
}
```

**Response**:

```json
{
  "taskType": "videoInference",
  "taskUUID": "f92a00b4-442e-4981-9878-a8bf9bdb2554",
  "videoUUID": "f9dd6d51-28f2-406f-a9d2-32bf0f53cd55",
  "videoURL": "https://vm.runware.ai/video/os/a17d13/ws/5/vi/f9dd6d51-28f2-406f-a9d2-32bf0f53cd55.mp4",
  "cost": 0.24
}
```