Name: SDXL Lightning API: Fast 4-Step Text to Image
Brand: magicapi
SKU: api-magicapi-fast-text-to-image-generator-bytedance-sdxl-lightning-4step
Availability: InStock
Author: API Market

Shashank Agarwal

# ⚡ Text-to-Image Generator API (ByteDance SDXL-Lightning 4-step)

## Overview
SDXL-Lightning is a text-to-image model from ByteDance. Its developer describes it as a fast text-to-image model that makes high-quality images in 4 steps.

Send a `prompt` and optionally a `negative_prompt`, the `width` and `height` (256 to 1280 pixels, default 1024), the number of images (`num_outputs`, 1 to 4) and a `seed`. The response is a list of image URLs.

## Features
- **4-step generation**: `num_inference_steps` defaults to 4, which the developer recommends for best results (range 1 to 10).
- **Custom size**: `width` and `height` from 256 to 1280 pixels; 1024 or 1280 is recommended.
- **Up to 4 images** per request with `num_outputs`.
- **Negative prompt**: defaults to `worst quality, low quality`.
- **Schedulers**: `K_EULER` (default), `DDIM`, `DPMSolverMultistep`, `HeunDiscrete`, `KarrasDPM`, `K_EULER_ANCESTRAL`, `PNDM`, `DPM++2MSDE`.
- **Seed**: set `seed` to reproduce a result.

## Use Cases
1. **Fast drafts**: quick concept images while iterating on a prompt.
2. **Interactive apps**: image generation where users wait for the result.
3. **Variations**: up to 4 images per request to pick from.
4. **Thumbnails and placeholders**: square or custom-size images for content and mockups.

## Visual Examples
### Example Input
A 1024 x 1024 portrait prompt with the default 4 steps:

```json
{
  "width": 1024,
  "height": 1024,
  "prompt": "self-portrait of a woman, lightning in the background",
  "scheduler": "K_EULER",
  "num_outputs": 1,
  "guidance_scale": 0,
  "negative_prompt": "worst quality, low quality",
  "num_inference_steps": 4
}
```

### Example Output
![SDXL-Lightning output: self-portrait of a woman with lightning in the background](https://blog.api.market/wp-content/uploads/2026/10/sdxl-lightning-4step-output-c2cpxjgj-api-market.jpg)

## Input Parameters
| Field | Type | Required | Default | Allowed values | Description |
| --- | --- | --- | --- | --- | --- |
| `prompt` | string | No | `self-portrait of a woman, lightning in the background` |  | Input prompt |
| `negative_prompt` | string | No | `worst quality, low quality` |  | Negative prompt: things to avoid in the image |
| `width` | integer | No | `1024` | `256` to `1280` | Width of output image. Recommended 1024 or 1280 |
| `height` | integer | No | `1024` | `256` to `1280` | Height of output image. Recommended 1024 or 1280 |
| `num_outputs` | integer | No | `1` | `1` to `4` | Number of images to output. |
| `scheduler` | string | No | `K_EULER` | `DDIM`, `DPMSolverMultistep`, `HeunDiscrete`, `KarrasDPM`, `K_EULER_ANCESTRAL`, `K_EULER`, `PNDM`, `DPM++2MSDE` | Scheduler |
| `num_inference_steps` | integer | No | `4` | `1` to `10` | Number of denoising steps. 4 for best results |
| `guidance_scale` | number | No | `0` | `0` to `50` | Scale for classifier-free guidance |
| `seed` | integer | No | `0` |  | Random seed. Leave blank to randomize the seed |
| `disable_safety_checker` | boolean | No | `false` |  | Disable safety checker for generated images |

## Pricing
- **Pay As You Go (PAYG) pricing**: you only pay for what you use.
- **Price**: $0.0032 per API unit.
- **1 API unit = 1 request with up to 2 seconds of processing time.** A request that runs longer uses one unit per started 2-second block.
- A single 1024 x 1024 image takes about 1 second, so it costs one unit ($0.0032). More images, larger sizes or more steps take longer and can use more units.
- **Example cost**: the example request took 1.02 seconds of processing = 1 unit = **$0.0032**.
- **Failed or cancelled predictions are not billed.**
- **GET requests to check prediction status** are free and don't count toward API unit usage.
- **No monthly subscription fee.**

## API Documentation

### Base URL
All API requests go to: `https://prod.api.market/api/v1/magicapi/fast-text-to-image-generator-bytedance-sdxl-lightning-4step`

### Authentication
Send your api.market API key in the `x-api-market-key` header:
```
x-api-market-key: YOUR_API_MARKET_KEY
```

### Asynchronous Processing
**IMPORTANT**: This API is asynchronous. The flow is:
1. Send a POST request to `/predictions`. A successful request returns **201 Created** with a prediction `id` and a `status` of `starting` or `processing`.
2. Poll GET `/predictions/{id}` with that ID.
3. Keep polling while `status` is `starting` or `processing`.
4. Stop when `status` is `succeeded` (read `output`), `failed` or `canceled` (read `error`).

A polling interval of 1 second and an overall timeout of 600 seconds (10 minutes) work well. The example finished in about 1 second.

### Endpoints

#### Create a Prediction
```bash
curl -X POST "https://prod.api.market/api/v1/magicapi/fast-text-to-image-generator-bytedance-sdxl-lightning-4step/predictions" \
  -H "Content-Type: application/json" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY" \
  -d '{
    "version": "6f7a773af6fc3e8de9d5a3c00be77c17308914bf67772726aff83496ba1e3bbe",
    "input": {
      "width": 1024,
      "height": 1024,
      "prompt": "self-portrait of a woman, lightning in the background",
      "scheduler": "K_EULER",
      "num_outputs": 1,
      "guidance_scale": 0,
      "negative_prompt": "worst quality, low quality",
      "num_inference_steps": 4
    }
  }'
```

Response (201 Created):
```json
{
  "id": "c2cpxjgj6xrnc0d1c6m9hhhmac",
  "version": "6f7a773af6fc3e8de9d5a3c00be77c17308914bf67772726aff83496ba1e3bbe",
  "status": "starting",
  "created_at": "2026-10-22T03:29:27.285Z"
}
```

#### Check Prediction Status
```bash
curl -X GET "https://prod.api.market/api/v1/magicapi/fast-text-to-image-generator-bytedance-sdxl-lightning-4step/predictions/{id}" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY"
```

Response when the prediction has finished (200 OK):
```json
{
  "id": "c2cpxjgj6xrnc0d1c6m9hhhmac",
  "status": "succeeded",
  "output": [
    "https://blog.api.market/wp-content/uploads/2026/10/sdxl-lightning-4step-output-c2cpxjgj-api-market.jpg"
  ],
  "error": null,
  "created_at": "2026-10-22T03:29:27.285Z",
  "started_at": "2026-10-22T03:29:27.485Z",
  "completed_at": "2026-10-22T03:29:28.312Z"
}
```

`output` is a list of image URLs, one per image (`num_outputs`).

### Status Codes
- **201 Created**: prediction created (POST `/predictions`). This is the normal success response.
- **200 OK**: prediction details returned (GET `/predictions/{id}`).
- **400 Bad Request**: invalid input, for example a `width` above 1280 or a `num_outputs` above 4.
- **401 Unauthorized**: missing or invalid API key.
- **404 Not Found**: no prediction with that ID.
- **429 Too Many Requests**: rate limit exceeded.
- **500 Internal Server Error** or **503 Service Unavailable**: temporary server problem; retry later.

## Rate Limits
All plans allow 10 requests per second. Requests above that return `429 Too Many Requests`; back off before retrying and honour any `Retry-After` header. Polling a prediction with GET is free but still counts toward the per-second limit, so poll every 1 to 5 seconds rather than in a tight loop.
## Error Handling
- Check the HTTP status code of every request and read the response body for the error message.
- A prediction can also end with `status` set to `failed`; the `error` field then explains why. Failed predictions are not billed.
- Retry 429, 500 and 503 responses with exponential backoff. Fix the input before retrying a 400.

## Implementation Guide
### Example Code

#### JavaScript
```javascript
const apiKey = "YOUR_API_MARKET_KEY";
const baseUrl = "https://prod.api.market/api/v1/magicapi/fast-text-to-image-generator-bytedance-sdxl-lightning-4step";

async function createAndWaitForPrediction(input) {
  const response = await fetch(`${baseUrl}/predictions`, {
    method: "POST",
    headers: {
      "Content-Type": "application/json",
      "x-api-market-key": apiKey
    },
    body: JSON.stringify({ version: "6f7a773af6fc3e8de9d5a3c00be77c17308914bf67772726aff83496ba1e3bbe", input })
  });

  if (response.status !== 201) {
    throw new Error(`API error: ${response.status} ${await response.text()}`);
  }

  const prediction = await response.json();
  return pollForResults(prediction.id);
}

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

async function pollForResults(predictionId) {
  const maxTimeout = 600000;
  const pollInterval = 1000;
  const startTime = Date.now();

  while (Date.now() - startTime < maxTimeout) {
    const response = await fetch(`${baseUrl}/predictions/${predictionId}`, {
      headers: { "x-api-market-key": apiKey }
    });

    if (!response.ok) {
      throw new Error(`API error: ${response.status} ${await response.text()}`);
    }

    const prediction = await response.json();

    if (prediction.status === "succeeded") {
      return prediction.output;
    }

    if (prediction.status === "failed" || prediction.status === "canceled") {
      throw new Error(`Prediction ${prediction.status}: ${prediction.error || "Unknown error"}`);
    }

    await delay(pollInterval);
  }

  throw new Error("Prediction timed out after 10 minutes");
}

createAndWaitForPrediction({
    "width": 1024,
    "height": 1024,
    "prompt": "self-portrait of a woman, lightning in the background",
    "scheduler": "K_EULER",
    "num_outputs": 1,
    "guidance_scale": 0,
    "negative_prompt": "worst quality, low quality",
    "num_inference_steps": 4
  }).then((output) => console.log(output));
```

#### Python
```python
import time
import requests

API_KEY = "YOUR_API_MARKET_KEY"
BASE_URL = "https://prod.api.market/api/v1/magicapi/fast-text-to-image-generator-bytedance-sdxl-lightning-4step"


def create_and_wait_for_prediction(input_data):
    headers = {"Content-Type": "application/json", "x-api-market-key": API_KEY}
    response = requests.post(
        f"{BASE_URL}/predictions",
        headers=headers,
        json={"version": "6f7a773af6fc3e8de9d5a3c00be77c17308914bf67772726aff83496ba1e3bbe", "input": input_data},
    )

    if response.status_code != 201:
        raise Exception(f"API error: {response.status_code} {response.text}")

    return poll_for_results(response.json()["id"])


def poll_for_results(prediction_id):
    max_timeout = 600
    poll_interval = 1
    headers = {"x-api-market-key": API_KEY}
    start_time = time.time()

    while time.time() - start_time < max_timeout:
        response = requests.get(f"{BASE_URL}/predictions/{prediction_id}", headers=headers)

        if response.status_code != 200:
            raise Exception(f"API error: {response.status_code} {response.text}")

        prediction = response.json()

        if prediction["status"] == "succeeded":
            return prediction["output"]

        if prediction["status"] in ("failed", "canceled"):
            raise Exception(f"Prediction {prediction['status']}: {prediction.get('error') or 'Unknown error'}")

        time.sleep(poll_interval)

    raise Exception("Prediction timed out after 10 minutes")


print(create_and_wait_for_prediction({
    "width": 1024,
    "height": 1024,
    "prompt": "self-portrait of a woman, lightning in the background",
    "scheduler": "K_EULER",
    "num_outputs": 1,
    "guidance_scale": 0,
    "negative_prompt": "worst quality, low quality",
    "num_inference_steps": 4
}))
```

## FAQ
- **How many images can I get per request?**
  - Up to 4, set with `num_outputs`. The response is a list with one URL per image.
- **How is a request billed?**
  - By processing time: $0.0032 covers up to 2 seconds, and longer requests use one unit per started 2-second block. The example (one 1024 x 1024 image) took about 1 second.
- **Should I change `num_inference_steps`?**
  - The model is built for 4 steps, which is the default and the developer's recommendation.
- **What sizes are supported?**
  - Any `width` and `height` from 256 to 1280 pixels; 1024 or 1280 is recommended.
- **Is the 201 response from POST an error?**
  - No. 201 Created means the prediction was accepted. Use the returned `id` to poll GET `/predictions/{id}` until `status` is `succeeded`, `failed` or `canceled`.
- **What if my prediction fails?**
  - Failed predictions are not billed. Read the `error` field, adjust the input and try again.

## Contact Us
If you have any questions or need assistance, you can reach out to us through the embedded chat on the bottom right corner of the page or send an email to hello@magicapi.com.


SDXL Lightning API by ByteDance: generate images from text in 4 steps, 256 to 1280 pixels per side and up to 4 images per request. Low cost, pay as you go.