Flux Dev Ultra Fast API Documentation

Flux Dev Ultra Fast API Documentation

Playground

FLUX.1 [dev] is a 12B rectified-flow transformer for high-quality text-to-image generation, optimized for ultra-fast inference. Ready-to-use REST inference API, best performance, no coldstarts, affordable pricing.

Features

FLUX Dev Ultra Fast is a lightweight, high-speed image generation and editing model built for rapid iteration. It supports both text-to-image generation and image-guided editing (image-to-image), with optional mask-based localized edits for targeted changes. This model is ideal when you need quick creative exploration, bulk variants, or fast prompt testing while maintaining strong visual quality.

Key capabilities

• Text-to-image generation for fast concepting
• Image-to-image editing for guided variations
• Masked editing (inpainting-style) for localized changes
• Adjustable strength to control how closely results follow the input image
• Custom output size, seed control, and standard image formats
• Efficient for high-volume runs and rapid experimentation

Use cases

• Rapid creative iterations for ads, thumbnails, and social content
• Style and composition exploration with quick turnaround
• Background swaps and wardrobe edits using a mask
• Product mockups and marketing variations (colorways, materials, packaging)
• Portrait enhancement workflows where speed matters (non-destructive variations)

Pricing

Inputs

• prompt (required): what to generate or how to edit
• image (optional): source image for image-to-image guidance
• mask_image (optional): region mask for localized edits

Parameters

• strength: how strongly the output is allowed to deviate from the input image (only for image-to-image)
• width / height: output size (e.g., 1024×1024)
• num_inference_steps: sampling steps
• guidance_scale: prompt adherence strength
• num_images: number of images to generate per run
• seed: random seed (-1 for random; set for reproducible results)
• output_format: jpeg / png / webp, etc.
• enable_base64_output: return BASE64 instead of URL (API only)
• enable_sync_mode: wait for upload and return directly (API only)

Prompting tips

• For photoreal shots, specify lens/lighting and keep subject details explicit.
• For edits, describe the change clearly and rely on the input image to preserve identity and layout.
• If using a mask, focus the prompt on what should change inside the masked region.

Example prompts

• A young couple standing side by side at a traditional wedding ceremony, warm smiles, intricate embroidered attire, realistic lighting, shallow depth of field, ultra-detailed, natural skin texture.
• Edit: keep the same pose and background, change the clothing to a modern black suit and white dress, clean studio lighting, photorealistic.

Authentication

For authentication details, please refer to the Authentication Guide.

API Endpoints

Submit Task & Query Result

set -euo pipefail

export WAVESPEED_API_KEY="your-api-key"

REQUEST_BODY=$(cat <<'JSON'
{
  "prompt": "A cinematic ocean wave at sunrise, highly detailed",
  "strength": 0.8,
  "size": "1024*1024",
  "num_inference_steps": 28,
  "guidance_scale": 3.5,
  "num_images": 1,
  "output_format": "jpeg"
}
JSON
)

# 1. Submit the prediction once. Never retry this request automatically:
# a retry after an unclear failure can create a second, billed task.
CHECK='The task may already exist. Check History or the predictions list before submitting again.'
if ! SUBMIT_RESPONSE=$(curl --silent --show-error --fail-with-body \
  --connect-timeout 10 --max-time 60 \
  -X POST "https://api.wavespeed.ai/api/v3/wavespeed-ai/flux-dev-ultra-fast" \
  -H "Authorization: Bearer ${WAVESPEED_API_KEY}" \
  -H "Content-Type: application/json" \
  -d "${REQUEST_BODY}"); then
  printf 'Submit failed. %s\n' "${CHECK}" >&2
  exit 1
fi

TASK=$(printf '%s' "${SUBMIT_RESPONSE}" | jq 'if type == "object" and has("data") then .data else . end')
PREDICTION_ID=$(printf '%s' "${TASK}" | jq -r '.id // empty')
if [ -z "${PREDICTION_ID}" ]; then
  printf 'Submission response did not contain a prediction id. %s\n' "${CHECK}" >&2
  exit 1
fi
RESULT_URL="https://api.wavespeed.ai/api/v3/predictions/${PREDICTION_ID}/result"

# 2. Poll until the prediction reaches a final status.
BODY_FILE=$(mktemp)
trap 'rm -f "${BODY_FILE}"' EXIT
while true; do
  # Transient errors (429, 5xx) are retried, honoring Retry-After.
  HTTP_CODE=$(curl --silent --show-error --fail-with-body \
    --connect-timeout 10 --max-time 60 --retry 5 --retry-delay 2 \
    --output "${BODY_FILE}" --write-out '%{http_code}' \
    "${RESULT_URL}" \
    -H "Authorization: Bearer ${WAVESPEED_API_KEY}" || true)
  case "${HTTP_CODE}" in
    2??) ;;
    000|429|5??)  # dropped connection or temporary error: keep polling
      printf 'Task %s: HTTP %s, polling again in 10s\n' "${PREDICTION_ID}" "${HTTP_CODE}" >&2
      sleep 10; continue ;;
    *) printf 'Task %s: HTTP %s\n' "${PREDICTION_ID}" "${HTTP_CODE}" >&2
      cat "${BODY_FILE}" >&2; exit 1 ;;
  esac
  RESULT=$(jq 'if type == "object" and has("data") then .data else . end' "${BODY_FILE}")
  STATUS=$(printf '%s' "${RESULT}" | jq -r '.status // empty')

  case "${STATUS}" in
    completed) printf '%s\n' "${RESULT}" | jq '.outputs'; break ;;
    failed|cancelled|timeout|deleted)
      printf 'Task %s ended with status %s\n' "${PREDICTION_ID}" "${STATUS}" >&2
      printf '%s\n' "${RESULT}" | jq . >&2; exit 1 ;;
    *) sleep 2 ;;
  esac
done

Parameters

Task Submission Parameters

Request Parameters

Every model also accepts the global request options enable_sync_mode and enable_base64_output; see their pages for details.

Response Parameters

Result Request Parameters

Result Response Parameters