Name: FLUX PuLID API: Face ID Image Generator by ByteDance
Brand: magicapi
SKU: api-magicapi-contrastive-id-customization-bytedance-flux-pulid
Availability: InStock
Author: API Market

Shashank Agarwal

# 🎭 Face ID Image Generator API (ByteDance FLUX PuLID)

## Overview
FLUX PuLID is ByteDance's identity customization method for the FLUX-dev image model. PuLID stands for Pure and Lightning ID customization via contrastive alignment. You give it one face photo and a text prompt, and it generates new images of that person in the scene you describe.

Send a `main_face_image` (required) and a `prompt`. Each request returns a list of 1 to 4 image URLs (`num_outputs`).

## Features
- **Identity from one photo**: a single `main_face_image` sets the face that appears in the generated images.
- **Identity strength**: `id_weight` (0 to 3, default 1) sets how strongly the face image influences the result.
- **Fidelity or editability**: `start_step` (0 to 10) sets when the identity is inserted. The model recommends 0 to 4: 0 for the highest fidelity to the face, 4 for more freedom to follow the prompt.
- **Up to 4 images per request**: set `num_outputs` from 1 to 4.
- **Sizes from 256 to 1536 pixels**: set `width` (default 896) and `height` (default 1152).
- **Guidance controls**: `guidance_scale` (1 to 10) and `true_cfg` (1 to 10; values above 1 enable true CFG for closer prompt adherence at some cost to image quality).
- **Output format**: `webp` (default), `jpg` or `png`, with `output_quality` 1 to 100 for jpg and webp.

## Use Cases
1. **Personalized portraits**: place a person in different settings, outfits and styles from one photo.
2. **Avatars and profile images**: generate consistent images of the same face for profiles or apps.
3. **Storyboards and character sheets**: keep one person's identity across several scenes.
4. **Marketing visuals**: show the same model or spokesperson in several product scenes.

## Visual Examples
### Example Input
Face image:

![Input face photo used as main_face_image](https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-input-api-market.png)

```json
{
  "width": 896,
  "height": 1152,
  "prompt": "a woman holding sign with glowing green text \"PuLID for FLUX\"",
  "true_cfg": 1,
  "id_weight": 1,
  "num_steps": 20,
  "start_step": 4,
  "num_outputs": 4,
  "output_format": "webp",
  "guidance_scale": 4,
  "output_quality": 80,
  "main_face_image": "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-input-api-market.png",
  "negative_prompt": "bad quality, worst quality, text, signature, watermark, extra limbs",
  "max_sequence_length": 128
}
```

### Example Output
The request asked for 4 images:

![FLUX PuLID output 1: the input face holding a sign with glowing green text](https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-1-g0ha70e9-api-market.webp)
![FLUX PuLID output 2: the input face holding a sign with glowing green text](https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-2-g0ha70e9-api-market.webp)
![FLUX PuLID output 3: the input face holding a sign with glowing green text](https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-3-g0ha70e9-api-market.webp)
![FLUX PuLID output 4: the input face holding a sign with glowing green text](https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-4-g0ha70e9-api-market-1.webp)

## Input Parameters
| Field | Type | Required | Default | Allowed values | Description |
| --- | --- | --- | --- | --- | --- |
| `main_face_image` | string (URL) | Yes |  |  | ID image for face generation. Image URL (jpeg, png, gif or webp). |
| `prompt` | string | No | `portrait, color, cinematic` |  | Text prompt to guide image generation |
| `negative_prompt` | string | No | `bad quality, worst quality, text, signature, watermark, extra limbs, low resolution, partially rendered objects, deformed or partially rendered eyes, deformed, deformed eyeballs, cross-eyed, blurry` |  | What to avoid in the image |
| `width` | integer | No | `896` | 256 to 1536 | Width of the generated image in pixels |
| `height` | integer | No | `1152` | 256 to 1536 | Height of the generated image in pixels |
| `num_steps` | integer | No | `20` | 1 to 20 | Number of denoising steps |
| `start_step` | integer | No | `0` | 0 to 10 | Timestep to start inserting the ID. 0 to 4 recommended: 0 for highest fidelity, 4 for more editability. |
| `guidance_scale` | number | No | `4` | 1 to 10 | Guidance scale for text prompt influence |
| `id_weight` | number | No | `1` | 0 to 3 | Weight of the ID image influence |
| `seed` | integer | No | none |  | Random seed for generation. Leave blank or use -1 for random. |
| `true_cfg` | number | No | `1` | 1 to 10 | Classifier-free guidance scale. 1.0 uses standard CFG; values above 1.0 enable true CFG for more precise control. Higher values increase prompt adherence at the cost of image quality. |
| `max_sequence_length` | integer | No | `128` | 128 to 512 | Maximum prompt sequence length (T5). Smaller is faster. |
| `output_format` | string | No | `webp` | `png`, `jpg`, `webp` | Format of the output images |
| `output_quality` | integer | No | `80` | 1 to 100 | Quality of the output images for jpg and webp |
| `num_outputs` | integer | No | `1` | 1 to 4 | Number of images to generate |

## Pricing
- **Pay As You Go (PAYG) pricing**: you only pay for what you use.
- **Price**: $0.022 per API unit.
- **1 API unit = 1 request covering up to 14 seconds of processing.** A request that processes for longer uses one unit per started 14-second block (for example 15 seconds = 2 units, $0.044). Each extra output, more steps and larger sizes add processing time.
- **Example cost**: the example request generated 4 images and processed for 39.26 seconds = 3 API units = **$0.066**.
- **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/contrastive-id-customization-bytedance-flux-pulid`

### 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.

### Endpoints

#### Create a Prediction
```bash
curl -X POST "https://prod.api.market/api/v1/magicapi/contrastive-id-customization-bytedance-flux-pulid/predictions" \
  -H "Content-Type: application/json" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY" \
  -d '{
    "version": "8baa7ef2255075b46f4d91cd238c21d31181b3e6a864463f967960bb0112525b",
    "input": {
      "width": 896,
      "height": 1152,
      "prompt": "a woman holding sign with glowing green text \"PuLID for FLUX\"",
      "true_cfg": 1,
      "id_weight": 1,
      "num_steps": 20,
      "start_step": 4,
      "num_outputs": 4,
      "output_format": "webp",
      "guidance_scale": 4,
      "output_quality": 80,
      "main_face_image": "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-input-api-market.png",
      "negative_prompt": "bad quality, worst quality, text, signature, watermark, extra limbs",
      "max_sequence_length": 128
    }
  }'
```

Response (201 Created):
```json
{
  "id": "g0ha70e9qxrna0d1ccjbs0xkc4",
  "version": "8baa7ef2255075b46f4d91cd238c21d31181b3e6a864463f967960bb0112525b",
  "status": "starting",
  "created_at": "2026-10-22T10:25:17.927Z"
}
```

#### Check Prediction Status
```bash
curl -X GET "https://prod.api.market/api/v1/magicapi/contrastive-id-customization-bytedance-flux-pulid/predictions/{id}" \
  -H "x-api-market-key: YOUR_API_MARKET_KEY"
```

Response when the prediction has finished (200 OK):
```json
{
  "id": "g0ha70e9qxrna0d1ccjbs0xkc4",
  "status": "succeeded",
  "output": [
    "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-1-g0ha70e9-api-market.webp",
    "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-2-g0ha70e9-api-market.webp",
    "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-3-g0ha70e9-api-market.webp",
    "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-output-4-g0ha70e9-api-market-1.webp"
  ],
  "error": null,
  "created_at": "2026-10-22T10:25:17.927Z",
  "started_at": "2026-10-22T10:25:17.942Z",
  "completed_at": "2026-10-22T10:25:57.199Z"
}
```

`output` is a list of image URLs, one per requested output (`num_outputs`), in the chosen `output_format`.

### 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 missing `main_face_image` or a `width` outside 256 to 1536.
- **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/contrastive-id-customization-bytedance-flux-pulid";

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: "8baa7ef2255075b46f4d91cd238c21d31181b3e6a864463f967960bb0112525b", 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: 896,
  height: 1152,
  prompt: "a woman holding sign with glowing green text \"PuLID for FLUX\"",
  true_cfg: 1,
  id_weight: 1,
  num_steps: 20,
  start_step: 4,
  num_outputs: 4,
  output_format: "webp",
  guidance_scale: 4,
  output_quality: 80,
  main_face_image: "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-input-api-market.png",
  negative_prompt: "bad quality, worst quality, text, signature, watermark, extra limbs",
  max_sequence_length: 128
}).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/contrastive-id-customization-bytedance-flux-pulid"


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": "8baa7ef2255075b46f4d91cd238c21d31181b3e6a864463f967960bb0112525b", "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": 896,
    "height": 1152,
    "prompt": "a woman holding sign with glowing green text \"PuLID for FLUX\"",
    "true_cfg": 1,
    "id_weight": 1,
    "num_steps": 20,
    "start_step": 4,
    "num_outputs": 4,
    "output_format": "webp",
    "guidance_scale": 4,
    "output_quality": 80,
    "main_face_image": "https://blog.api.market/wp-content/uploads/2026/10/flux-pulid-input-api-market.png",
    "negative_prompt": "bad quality, worst quality, text, signature, watermark, extra limbs",
    "max_sequence_length": 128
}))
```

## FAQ
- **What kind of face photo works best?**
  - Send one clear photo of a single face as `main_face_image`. The identity of that face is carried into every generated image.
- **The result looks too much like the original photo. How do I give the prompt more room?**
  - Raise `start_step` (up to 4 is recommended) or lower `id_weight`. Use `start_step` 0 when fidelity to the face matters most.
- **How many images does one request return?**
  - Between 1 and 4, set by `num_outputs` (default 1). Billing is by processing time, so 4 images usually cost more than 1: the example with 4 images took 3 API units ($0.066).
- **What is the difference between `guidance_scale` and `true_cfg`?**
  - `guidance_scale` sets how strongly the text prompt guides generation. `true_cfg` at 1.0 uses standard CFG; values above 1.0 enable true CFG, which follows the prompt more closely at some cost to image quality.
- **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`.

## Contact Us
If you have any questions, reach out to us through the chat on the bottom right of the page. You can also email our support team at hello@magicapi.com.


Turn one face photo and a text prompt into up to 4 new images of the same person with ByteDance FLUX PuLID. $0.022 per 14 seconds of processing, pay as you go.