---
title: LTX-2.5 Fast | Runware Docs
url: https://runware.ai/docs/models/lightricks-ltx-2-5-fast
description: Fast high-resolution video generation with longer clip support, native audio, and first-to-last-frame control
---
# LTX-2.5 Fast

LTX-2.5 Fast is the speed-focused variant in the LTX 2.5 video family, built for high-throughput text-to-video and image-to-video generation. It supports output from 720p through 4K, longer durations at HD resolutions, optional native audio generation, and first-to-last-frame image guidance for more directed motion and shot planning. It is well suited to rapid creative iteration, storyboard development, social and advertising content, and other video workflows that need faster turnaround without dropping to low-end resolutions.

- **ID**: `lightricks:ltx@2.5-fast`
- **Status**: live
- **Creator**: Lightricks
- **Release Date**: August 11, 2026
- **Capabilities**: Text to Video, Image to Video, Checkpoint

## Compatibility & Validation

When `fps` is `48, or 50`, `duration` must be at most `10`.

---

Inside `inputs`, `frameImages` cannot be used with `audio`.

---

When `inputs.audio` is provided, `duration` and `settings.cameraMovement` cannot be used.

---

When `inputs.audio` is provided, `inputs.referenceImages` is required.

---

When `inputs.referenceImages` is provided, `inputs.audio` is required.

---

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

---

When `width` or `height` is provided, `duration` must be at most `10`.

---

The following dimension combinations are supported:

| Dimensions |
| --- |
| `1920x1080` |
| `1080x1920` |

| Configuration | Dimensions |
| --- | --- |
| `720p (16:9)` | `1280x720` |
| `720p (9:16)` | `720x1280` |
| `1080p (16:9)` | `1920x1080` |
| `1080p (9:16)` | `1080x1920` |
| `2K (16:9)` | `2560x1440` |
| `2K (9:16)` | `1440x2560` |
| `4K (16:9)` | `3840x2160` |
| `4K (9:16)` | `2160x3840` |

## Notes

LTX-2.5 Fast decides what to generate from the input you attach:

- **Text-to-Video:** Provide a prompt on its own.
- **Image-to-Video:** Provide `inputs.frameImages`. The first entry opens the clip and an optional second one closes it.
- **Audio-to-Video:** Provide `inputs.audio` together with a single `inputs.referenceImages` entry that establishes the subject. Frame images cannot be combined with audio.

**Duration:** Set `duration` to a whole number of seconds, or `auto` to let the model read the length from the prompt. A one-line action stays short and a multi-shot sequence runs longer, but the result never exceeds the ceiling for the resolution and frame rate you asked for.

Audio-driven output runs as long as the audio, so `duration` is not accepted on that path.

**Camera movement:** `settings.cameraMovement` applies a fixed camera move to the shot. It is available for text-to-video and image-to-video.

## Request Parameters

**API Options**

Platform-level options for task execution and delivery.

### [taskType](https://runware.ai/docs/models/lightricks-ltx-2-5-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-2-5-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-2-5-fast#request-outputtype)

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

Video output type.

**Allowed values**: `URL`

### [outputFormat](https://runware.ai/docs/models/lightricks-ltx-2-5-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-2-5-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-2-5-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-2-5-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-2-5-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-2-5-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-2-5-fast#request-safety-checkcontent)

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

Enable or disable content safety checking. Increases total generation time.

#### [mode](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-safety-mode)

- **Path**: `safety.mode`
- **Type**: `string`
- **Default**: `fast`

Safety checking mode for video generation.

**Allowed values**:

- `fast` Checks key frames.
- `full` Checks all frames.

### [ttl](https://runware.ai/docs/models/lightricks-ltx-2-5-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-2-5-fast#request-includecost)

- **Type**: `boolean`

Include task cost in the response.

### [numberResults](https://runware.ai/docs/models/lightricks-ltx-2-5-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.

### [referenceImages](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-inputs-referenceimages)

- **Path**: `inputs.referenceImages`
- **Type**: `array of strings`

List of reference images (UUID, URL, Data URI, or Base64).

### [frameImages](https://runware.ai/docs/models/lightricks-ltx-2-5-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 position in the video.

The `frameImages` parameter allows you to constrain specific frames within the video sequence, ensuring that particular visual content appears at designated points. Position can be specified using `frame` (named positions or frame indices) or `timestamp` (seconds), depending on model support. 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.
- **2 images**: First and last frames.

**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 position, use an object with `image` and either `frame` or `timestamp` (model-dependent).

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

**First and last frames:** With two images, they automatically become the first and last frames of the video sequence. You can mix shorthand and object formats.

```json
"frameImages": [
  "aac49721-1964-481a-ae78-8a4e29b91402",
  {
    "image": "3ad204c3-a9de-4963-8a1a-c3911e3afafe",
    "frame": "last"
  }
]
```

**Format 1: string[]**:

- **Type**: `string`

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

**Format 2: object[]**:

#### [image](https://runware.ai/docs/models/lightricks-ltx-2-5-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-2-5-fast#request-inputs-frameimages-format-2-frame)

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

Target frame position for the image. Supports first and last frame.

**Allowed values**:

- `first` First frame of the video.
- `last` Last frame of the video.
- `0` Frame index 0 (first frame).
- `-1` Frame index -1 (last frame).

### [audio](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-inputs-audio)

- **Path**: `inputs.audio`
- **Type**: `string`
- **Duration**: `2s to 20s`

Audio input (UUID or URL). Drives the generated video, whose length follows the audio.

**Core Parameters**

Primary parameters that define the task output.

### [model](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-model)

- **Type**: `string`
- **Required**: true
- **Value**: `lightricks:ltx@2.5-fast`

Identifier of the model to use for generation.

**Learn more** (3 resources):

- [Text To Image: Model Selection](https://runware.ai/docs/learn/text-to-image#model-selection) (learn)
- [Image Inpainting: Model Specialized Inpainting Models](https://runware.ai/docs/learn/image-inpainting#model-specialized-inpainting-models) (learn)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/learn/image-outpainting#other-critical-parameters) (learn)

### [positivePrompt](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-positiveprompt)

- **Type**: `string`
- **Required**: true
- **Min**: `2`
- **Max**: `5000`

Text prompt describing elements to include in the generated output.

**Learn more** (1 resource):

- [Prompts](https://runware.ai/docs/learn/prompts) (learn)

### [width](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-width)

- **Type**: `integer`
- **Required**: true
- **Default**: `1920`
- **Paired with**: height

Width of the generated media in pixels.

**Learn more** (2 resources):

- [Dimensions](https://runware.ai/docs/learn/dimensions) (learn)
- [Image Outpainting: Dimensions Critical For Outpainting](https://runware.ai/docs/learn/image-outpainting#dimensions-critical-for-outpainting) (learn)

### [height](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-height)

- **Type**: `integer`
- **Required**: true
- **Default**: `1080`
- **Paired with**: width

Height of the generated media in pixels.

**Learn more** (2 resources):

- [Dimensions](https://runware.ai/docs/learn/dimensions) (learn)
- [Image Outpainting: Dimensions Critical For Outpainting](https://runware.ai/docs/learn/image-outpainting#dimensions-critical-for-outpainting) (learn)

### [duration](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-duration)

- **Type**: `integer | string`
- **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).

**Allowed values**: `6` `8` `10` `12` `14` `16` `18` `20` `auto`

### [fps](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-fps)

- **Type**: `integer`

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-2-5-fast#request-settings-audio)

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

Generate synchronized audio.

### [cameraMovement](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#request-settings-cameramovement)

- **Path**: `settings.cameraMovement`
- **Type**: `string`

Cinematic camera movement.

**Allowed values**:

- `dolly_in` Camera moves toward the subject.
- `dolly_out` Camera moves away from the subject.
- `dolly_left` Camera tracks to the left.
- `dolly_right` Camera tracks to the right.
- `jib_up` Camera rises on a jib.
- `jib_down` Camera lowers on a jib.
- `static` Fixed camera with no movement.
- `focus_shift` Focus racks between subjects.

## Response Parameters

### [taskType](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-tasktype)

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

Identifier for the type of task this response belongs to.

### [taskUUID](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-taskuuid)

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

UUID v4 identifier echoed from the original request, used to match async responses to their tasks.

### [videoUUID](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-videouuid)

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

UUID of the output video.

### [videoURL](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-videourl)

- **Type**: `string`
- **Format**: `uri`

URL of the output video.

### [videoBase64Data](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-videobase64data)

- **Type**: `string`

Base64-encoded video data.

### [videoDataURI](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-videodatauri)

- **Type**: `string`
- **Format**: `uri`

Data URI of the output video.

### [seed](https://runware.ai/docs/models/lightricks-ltx-2-5-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-2-5-fast#response-nsfwcontent)

- **Type**: `boolean`

Flag indicating if NSFW content was detected.

### [cost](https://runware.ai/docs/models/lightricks-ltx-2-5-fast#response-cost)

- **Type**: `float`

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

## Examples

### Arctic Seed Vault Title Sequence (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/0139c178-ae86-433a-bf2c-b1e00874bc24.mp4)

---

### Glassworks Techno Lyric Video (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/188318c1-d036-4281-a544-151c60ee7f6a.mp4)

---

### Sculptural Hearing Jewelry Product Reel (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/faecc67f-8e34-4a6f-b118-5e827f848acc.mp4)

---

### Battery Recycling Safety Presenter (Image to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/c6f752ff-51ac-45b8-8f98-e56cb87705ae.mp4)

---

### Reflective Cycling Cape Fashion Reel (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/67aa2349-2166-4d11-97b2-82cf2406b32e.mp4)

---

### Transplant Courier Series Title Teaser (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/5f5f6493-6443-4404-882d-83ec69fd69a0.mp4)

---

### Satellite Risk Underwriter Briefing (Image to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/587d4be1-c917-42e3-bdc0-68c398396779.mp4)

---

### Artisan Paper Marbling Workshop Reel (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/b06f865b-7483-49f2-a5c6-ef2ed93c9ec6.mp4)

---

### Midnight Flower Market Music Segment (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/0b86decd-d949-40fc-8769-6d8ede2ed4ef.mp4)

---

### Couture Falconry Glove Showcase Reel (Image to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/0a8cc329-c417-4527-8458-4ae8b965bcaa.mp4)

---

### Rare Manuscript Training Presenter Clip (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/1c89ac47-274e-47cc-b130-1933198c07cb.mp4)

---

### Smart Irrigation Valve Cutaway Demo (Text to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/24f2d72e-af52-4935-b388-919b8f0e1610.mp4)

---

### Runway Rubber Removal B-Roll (Image to Video)

[Watch video](https://assets.runware.ai/examples/lightricks-ltx-2-5-fast/cf6e3840-e0a1-4c12-8993-b9242254c84c.mp4)