About FLUX 3 Klein
Fast FLUX 3 Klein images and multi-reference edits at 1K or 2K.
Call it with the model name black-forest-labs/flux-3-klein/text-to-image on POST /jobs/createTask, from $0.012.
Request parameters
| Parameter | Required | Description |
|---|---|---|
seed | No | Reuse the same number to get a repeatable result. ≥ 0 · ≤ 2147483647 |
width | No | Output width in pixels when aspect_ratio is custom, 256 to 1024 (1024 if left out); height works the same way. The price still follows resolution. ≥ 256 · ≤ 1024 |
height | No | Output height in pixels when aspect_ratio is custom, 256 to 1024 (1024 if left out); width works the same way. The price still follows resolution. ≥ 256 · ≤ 1024 |
prompt | Yes | Describe the subject, setting, light and style in plain sentences. |
resolution | No | Output size. Bigger sizes look sharper and cost more. 1k · 2k · Default: 1k |
aspect_ratio | No | The shape of the frame: wide, square or tall. 1:1 · 16:9 · 9:16 · 4:3 · 3:4 · 3:2 · 2:3 · 4:5 · 5:4 · 21:9 · 9:21 · 2:1 · 1:2 · 3:1 · 1:3 · custom · Default: 1:1 |
output_format | No | File type of the result. jpeg · png · webp · Default: jpeg |
enable_prompt_expansion | No | Lets the model add detail to a short prompt. Default: false |
Pricing
Prices are in USD. The API uses a separate USD balance. Website credits cannot be used or transferred to it, and API funds cannot be transferred to website credits. When a task is accepted, we reserve the maximum quoted amount from your API balance. On completion, we charge for actual usage, never more than the hold, and release the remainder. If the task fails, the hold is released.
| Option | USD per image |
|---|---|
| resolution 1K | $0.012 |
| resolution 2K | $0.048 |
Send the same request body to POST /jobs/quote to see the estimated and maximum USD charge before running. A quote does not run the task or charge your balance.
API quick start
Call the FLUX 3 Klein API in three steps
- Create an API key. Sign in to PopNow and create a key in the API console. Keys start with sk-popnow-. API calls use your separate USD balance.
- Send the request. POST /jobs/createTask with model black-forest-labs/flux-3-klein/text-to-image and an input object that follows the parameter table. The response returns a task ID straight away.
- Get the result. Poll GET /jobs/recordInfo with the task ID, or pass a callBackUrl and we post the result to it. Download the output links when the task succeeds.
# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
-H "Authorization: Bearer $POPNOW_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: $IDEMPOTENCY_KEY" \
-d '{
"model": "black-forest-labs/flux-3-klein/text-to-image",
"input": {
"prompt": "A ceramic teapot on a linen cloth, soft window light, muted palette",
"aspect_ratio": "1:1",
"resolution": "1k",
"output_format": "jpeg"
}
}'
# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
-H "Authorization: Bearer $POPNOW_API_KEY"Replace the prompt and any links with your own. The API tab has the response, polling and callback reference.
FLUX 3 Klein API questions
How much does the FLUX 3 Klein API cost?
FLUX 3 Klein starts at $0.012 per image with Create Image, its cheapest task. Prices by option: 1K $0.012 per image, 2K $0.048 per image. The API uses a separate USD balance. Website credits cannot be used or transferred to it, and API funds cannot be transferred to website credits. When a task is accepted, we reserve the maximum quoted amount from your API balance. On completion, we charge for actual usage, never more than the hold, and release the remainder. If the task fails, the hold is released.
What is the model name for FLUX 3 Klein in the API?
Put black-forest-labs/flux-3-klein/text-to-image for Create Image; black-forest-labs/flux-3-klein/edit for Edit Image in the model field of POST /jobs/createTask.
What are the limits of the FLUX 3 Klein API?
Resolutions: 1K · 2K; Aspect ratios: 1:1 · 16:9 · 9:16 · 4:3 · 3:4 · 3:2 +10; Prompt length (characters): 5,000. Requests outside these limits are rejected before anything is charged.
More about FLUX 3 Klein
- Endpoints
- FLUX 3 Klein · Edit Image