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Flux 2 Flex Text to Image

fal-ai/flux-2-flex
Text-to-image generation with FLUX.2 [flex] from Black Forest Labs. Features adjustable inference steps and guidance scale for fine-tuned control. Enhanced typography and text rendering capabilities.
Inference
Commercial use
Partner
Schema
LLMs
PlaygroundAPI

About

Text To Image

1. Calling the API#

Install the client#

The client provides a convenient way to interact with the model API.

npm install --save @fal-ai/client

Setup your API Key#

Set FAL_KEY as an environment variable in your runtime.

export FAL_KEY="YOUR_API_KEY"

Submit a request#

The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.

import { fal } from "@fal-ai/client";

const result = await fal.subscribe("fal-ai/flux-2-flex", {
  input: {
    prompt: "A high-quality 3D render of a cute fluffy monster eating a giant donut; the fur simulation is incredibly detailed, the donut glaze is sticky and reflective, bright daylight lighting, shallow depth of field."
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);

2. Authentication#

The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.

API Key#

In case your app is running in an environment where you cannot set environment variables, you can set the API Key manually as a client configuration.
import { fal } from "@fal-ai/client";

fal.config({
  credentials: "YOUR_FAL_KEY"
});

3. Queue#

Submit a request#

The client API provides a convenient way to submit requests to the model.

import { fal } from "@fal-ai/client";

const { request_id } = await fal.queue.submit("fal-ai/flux-2-flex", {
  input: {
    prompt: "A high-quality 3D render of a cute fluffy monster eating a giant donut; the fur simulation is incredibly detailed, the donut glaze is sticky and reflective, bright daylight lighting, shallow depth of field."
  },
  webhookUrl: "https://optional.webhook.url/for/results",
});

Fetch request status#

You can fetch the status of a request to check if it is completed or still in progress.

import { fal } from "@fal-ai/client";

const status = await fal.queue.status("fal-ai/flux-2-flex", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
  logs: true,
});

Get the result#

Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.

import { fal } from "@fal-ai/client";

const result = await fal.queue.result("fal-ai/flux-2-flex", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);

4. Files#

Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.

Data URI (base64)#

You can pass a Base64 data URI as a file input. The API will handle the file decoding for you. Keep in mind that for large files, this alternative although convenient can impact the request performance.

Hosted files (URL)#

You can also pass your own URLs as long as they are publicly accessible. Be aware that some hosts might block cross-site requests, rate-limit, or consider the request as a bot.

Uploading files#

We provide a convenient file storage that allows you to upload files and use them in your requests. You can upload files using the client API and use the returned URL in your requests.

import { fal } from "@fal-ai/client";

const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);

Read more about file handling in our file upload guide.

5. Schema#

Input#

prompt string* required

The prompt to generate an image from.

image_size ImageSize | Enum

The size of the generated image. Default value: landscape_4_3

Possible enum values: square_hd, square, portrait_4_3, portrait_16_9, landscape_4_3, landscape_16_9

Note: For custom image sizes, you can pass the width and height as an object:

"image_size": {
  "width": 1280,
  "height": 720
}
enable_prompt_expansion boolean

Whether to expand the prompt using the model's own knowledge.

seed integer

The seed to use for the generation.

enable_safety_checker boolean

Whether to enable the safety checker. Default value: true

output_format OutputFormatEnum

The format of the generated image. Default value: "jpeg"

Possible enum values: jpeg, png

sync_mode boolean

If True, the media will be returned as a data URI and the output data won't be available in the request history.

guidance_scale float

The guidance scale to use for the generation. Default value: 3.5

num_inference_steps integer

The number of inference steps to perform. Default value: 28

{
  "prompt": "A high-quality 3D render of a cute fluffy monster eating a giant donut; the fur simulation is incredibly detailed, the donut glaze is sticky and reflective, bright daylight lighting, shallow depth of field.",
  "image_size": "landscape_4_3",
  "enable_safety_checker": true,
  "output_format": "jpeg",
  "guidance_scale": 3.5,
  "num_inference_steps": 28
}

Output#

images list<ImageFile>* required

The generated images.

seed integer* required

The seed used for the generation.

{
  "images": [
    {
      "url": "https://storage.googleapis.com/falserverless/example_outputs/flux2_flex_t2i_output.png"
    }
  ]
}

Other types#

ImageFile#

url string* required

The URL where the file can be downloaded from.

content_type string

The mime type of the file.

file_name string

The name of the file. It will be auto-generated if not provided.

file_size integer

The size of the file in bytes.

width integer

The width of the image

height integer

The height of the image

ImageSize#

width integer

The width of the generated image. Default value: 512

height integer

The height of the generated image. Default value: 512

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