Flux 2 Flex Text to Image

bfl/flux-2/flex

Flux 2 Flex is BFL's advanced text-to-image AI model. Create photorealistic images, illustrations, and concept art from natural language descriptions with exceptional detail and prompt adherence.

Try the model

Playground

Open playground

Input

Prompt(string)

The prompt to generate an image from.

Additional Settings More

Customize your input with more control.

Guidance Scale(number)

1.510

The guidance scale to use for the generation. Range: 1.5 to 10.

Number of Inference Steps(integer)

250

The number of inference steps to perform. Range: 2 to 50.

Output Format(string)

The format of the generated image. Allowed values: jpeg, png.

Aspect Ratio(string)

The aspect ratio of the generated image. Allowed values: 21:9, 16:9, 3:2, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 9:16.

Seed(integer)

The seed to use for the generation.

Result

Example

What would you like to do next?
Open original

Examples

Select an example to load its inputs and result into the playground.

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."
}
```
Open result ↗

Human preference

Arena

Elo ratings from blind side-by-side votes, compared with other image and video models.

Rankings sourced from Artificial Analysis Arena

Leaderboard: Text to Image
Rank: #29 of 106
Elo: 1026 ±11
Gap to #1: −196

Text-to-image arena: people pick the better of two images generated from the same prompt, without seeing the model names.

#24Krea 2 LargeKrea1034±9
#25Qwen Image 2.0 Pro (2026-04-22)Alibaba1030±11
#26MAI-Image-2.5-FlashMicrosoft AI1029±11
#27Qwen-Image-2.1-TurboAlibaba1029±12
#28Wan 2.6 ImageAlibaba1027±12
#29FLUX.2 [flex]Black Forest LabsThis model1026±11
#30Ideogram 4.0 (Quality)Ideogram1026±10
#31Recraft V4.1 UtilityRecraftOn SandBase1026±11
#32Seedream 4.5ByteDance SeedOn SandBase1026±12
#33Luma UNI 1 MaxLuma Labs1023±12

Flux 2 Flex Text to Image

FLUX.2 [flex], the tunable tier: adjust steps and guidance for typography-heavy or detailed work. Text to image.

Fields

Field	Type	Default	Notes
`prompt`	string, required	—	Text instruction.
`guidance_scale`	number 1.5–10	3.5	How strictly to follow the prompt.
`num_inference_steps`	integer 2–50	28	More steps add detail and time.
`output_format`	`jpeg` / `png`	`jpeg`	Output file format.
`aspect_ratio`	`21:9` / `16:9` / `3:2` / `4:3` / `5:4` / `1:1` / `4:5` / `3:4` / `2:3` / `9:16`	`16:9`	Output shape.
`seed`	integer	random	Fix it to compare prompt changes.

Billing

$0.06 per image.

Request	Price
One image	$0.06

Failed runs are not charged.

Prompting

Write subject, setting, composition, style, then light.
Quote any text that must appear.

Limits

One output image per request.

Also on SandBase

Other FLUX.2 endpoints: bfl/flux-2/max, bfl/flux-2/pro, bfl/flux-2/dev, bfl/flux-2/turbo, bfl/flux-2/flex/edit.

Start building

Send your first request

Submit this model through the SandBase Unified Run API.

Production API

Unified Run API endpoint

https://api.sandbase.ai/v1/run

Model ID

bfl/flux-2/flex

# The quoted heredoc keeps Unicode and shell metacharacters unchanged.
result=$(curl --fail-with-body --silent \
  -X POST "https://api.sandbase.ai/v1/run" \
  -H "Authorization: Bearer $SANDBASE_API_KEY" \
  -H "Content-Type: application/json" \
  --data-binary @- <<'SANDBASE_JSON'
{
  "model": "bfl/flux-2/flex",
  "prompt": "A high-quality 3D render of a cute fluffy monster eating a giant donut; the fur simulation is incredibly detailed, the donut glaze is sticky and reflective, bright daylight lighting, shallow depth of field.",
  "aspect_ratio": "16:9",
  "output_format": "jpeg",
  "guidance_scale": 3.5,
  "num_inference_steps": 28
}
SANDBASE_JSON
)
run_id=$(printf '%s' "$result" | jq -r .id)
for attempt in $(seq 1 120); do
  status=$(printf '%s' "$result" | jq -r .status)
  case "$status" in completed|failed|timeout) break ;; esac
  sleep 2
  result=$(curl --fail-with-body --silent \
    -H "Authorization: Bearer $SANDBASE_API_KEY" \
    "https://api.sandbase.ai/v1/run/$run_id")
done
status=$(printf '%s' "$result" | jq -r .status)
[ "$status" = completed ] || { echo "Generation ended: $status" >&2; exit 1; }
printf '%s\n' "$result"

2. Authentication

Create a SandBase API key and set it in your server environment. All requests use Bearer authentication.

API key environment variable

export SANDBASE_API_KEY="YOUR_API_KEY"

Keep the key on your server. Do not expose it in browser code or commit it to a repository.

3. Queue

Submit a request

POST to /v1/run with this model ID and its inputs. The request example above includes submission and polling.

Fetch request status and result

Use the returned run ID to poll until the status is completed, failed or timeout. Read output only after completed.

Poll run status

curl "https://api.sandbase.ai/v1/run/$RUN_ID" \
  -H "Authorization: Bearer $SANDBASE_API_KEY"

4. Files

Hosted files

Pass a publicly accessible file URL in the model’s image, video or audio field. Supported formats and limits are shown beside each Playground input.

Uploading images

Use the upload or replace control on supported image fields in the Playground. Video URL fields accept a hosted driving video; they do not imply video-upload support.

5. Schema

Input

`seed`integer

The seed to use for the generation.

`prompt`stringrequired

The prompt to generate an image from.

`aspect_ratio`string

The aspect ratio of the generated image.

Default: "16:9"

Possible values: "21:9", "16:9", "3:2", "4:3", "5:4", "1:1", "4:5", "3:4", "2:3", "9:16"

`output_format`string

The format of the generated image.

Default: "jpeg"

Possible values: "jpeg", "png"

`guidance_scale`number

The guidance scale to use for the generation.

Default: 3.5

Minimum: 1.5

Maximum: 10

`num_inference_steps`integer

The number of inference steps to perform.

Default: 28

Minimum: 2

Maximum: 50

Request body

{
  "model": "bfl/flux-2/flex",
  "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.",
  "aspect_ratio": "16:9",
  "output_format": "jpeg",
  "guidance_scale": 3.5,
  "num_inference_steps": 28
}

Output

A completed run exposes its result in output. The following is the model’s saved example, not a new generation.

Example output JSON

[
  {
    "source": "BFL/FLUX schema mirror",
    "source_url": "https://docs.bfl.ai/flux_2/flux2_overview",
    "url": "https://static.sandbase.ai/examples/58485e7a-c0ff-4c8c-aef7-d56902fb9d44/output/8180b9ed-eb55-4342-aa81-aff730b8570f.png"
  }
]

Flux 2 Flex Text to Image

Playground

Examples

Arena

Flux 2 Flex Text to Image

Fields

Billing

Prompting

Limits

Also on SandBase

Send your first request

2. Authentication

3. Queue

Submit a request

Fetch request status and result

4. Files

Hosted files

Uploading images

5. Schema

Input

seedinteger

promptstringrequired

aspect_ratiostring

output_formatstring

guidance_scalenumber

num_inference_stepsinteger

Output

Flux 1 Schnell ↗

Flux 2 Dev Text to Image ↗

Flux 2 Flash Text to Image ↗

Flux 2 Klein 4B Text to Image ↗

Flux 2 Klein 9B Text to Image ↗

Flux 2 Max Text to Image ↗

`seed`integer

`prompt`stringrequired

`aspect_ratio`string

`output_format`string

`guidance_scale`number

`num_inference_steps`integer