Flux Kontext Dev | Fast Image Editing API

FLUX Kontext Dev — wavespeed-ai/flux-kontext-dev

FLUX.1 Kontext Dev is an open-weight, open-code image-to-image model built for instruction-based editing. Provide a source image plus a natural-language edit request, and the model rewrites the image while preserving the original context when asked—making it suitable for targeted retouching, object changes, background swaps, text edits, and controlled style transforms.

Key capabilities

Instruction-based image editing from a single input image
Strong subject and scene preservation when you explicitly request it
Local and global edits: change specific regions or the whole image
Iterative editing workflow: apply multiple edits step-by-step with minimal drift

Typical use cases

Retouching: lighting, exposure, cleanup, blemish removal
Object edits: add/remove/replace items, change colors/materials
Background replacement: swap environments while keeping the subject consistent
Text edits: add or replace words on signs, posters, packaging
Style transforms: convert to clay, illustration, cinematic, etc., while preserving composition

Pricing

$0.025 per image.

Cost per run = num_images × $0.025 Example: num_images = 4 → $0.10

Inputs and outputs

Input:

One source image (upload or public URL)
One edit instruction (prompt)

Output:

One or more edited images (controlled by num_images)

Parameters

prompt: Edit instruction describing what to change and what to keep
image: Source image
width / height: Output resolution
num_inference_steps: More steps usually improves quality but increases latency
guidance_scale: Higher values follow the prompt more strongly; too high may over-edit
num_images: Number of variations generated per run
seed: Fixed value for reproducibility; -1 for random
output_format: jpeg or png
enable_base64_output: Return BASE64 instead of a URL (API only)
enable_sync_mode: Wait for generation and return results directly (API only)

Prompting guide

Write prompts like an editor’s brief:

Preserve clause: what must stay the same
Edit clause: what must change
Constraints: realism level, lighting, placement, typography, materials
Consistency: match shadows/highlights to the new scene

Template: Keep [what must stay]. Change [what to edit]. Ensure [constraints]. Match [lighting/shadows/style consistency].

Example prompts

Keep the person’s face, pose, and clothing unchanged. Change the background to a foggy gothic castle. Match lighting and shadows to the new environment.
Change the car color to red. Preserve reflections and keep the rest of the scene unchanged.
Add the text “COOL” on the sign in the same perspective, with realistic shadows, and do not alter anything else.
Turn the image into a clay style with handcrafted texture and soft studio lighting, while keeping the composition and subject identity.
Remove the background crowd and keep the main subject sharp and unchanged.

Best practices

Start simple, then iterate: do one change per run for maximum control.
If the edit is too aggressive, lower guidance_scale and strengthen the preserve clause.
For A/B comparisons, keep seed fixed and change only one parameter at a time.
Use aspect-matched width/height to avoid unintended stretching.

Flux Kontext Dev API — Quick start

Grab a WaveSpeedAI API key, then call POST https://api.wavespeed.ai/api/v3/wavespeed-ai/flux-kontext-dev with your input as JSON. The endpoint returns a prediction id; poll the prediction endpoint until status flips to completed, then read the output URL from data.outputs[0]. Examples for Flux Kontext Dev below.

HTTP example

# Submit the prediction
curl -X POST "https://api.wavespeed.ai/api/v3/wavespeed-ai/flux-kontext-dev" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $WAVESPEED_API_KEY" \
  -d '{
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "image": "https://example.com/your-input.jpg",
    "num_inference_steps": 28,
    "guidance_scale": 2.5,
    "num_images": 1,
    "seed": -1,
    "output_format": "jpeg",
    "enable_base64_output": false,
    "enable_sync_mode": false
}'

# Response includes a prediction id. Poll for the result:
curl -X GET "https://api.wavespeed.ai/api/v3/predictions/{request_id}/result" \
  -H "Authorization: Bearer $WAVESPEED_API_KEY"

# When status is "completed", read the output from data.outputs[0].

Node.js example

// npm install wavespeed
const WaveSpeed = require('wavespeed');

const client = new WaveSpeed(); // reads WAVESPEED_API_KEY from env

const result = await client.run("wavespeed-ai/flux-kontext-dev", {
        "prompt": "A cinematic shot of a city at sunset, soft golden light",
        "image": "https://example.com/your-input.jpg",
        "num_inference_steps": 28,
        "guidance_scale": 2.5,
        "num_images": 1,
        "seed": -1,
        "output_format": "jpeg",
        "enable_base64_output": false,
        "enable_sync_mode": false
});

console.log(result.outputs[0]); // → URL of the generated output

Python example

# pip install wavespeed
import wavespeed

output = wavespeed.run(
    "wavespeed-ai/flux-kontext-dev",
    {
    "prompt": "A cinematic shot of a city at sunset, soft golden light",
    "image": "https://example.com/your-input.jpg",
    "num_inference_steps": 28,
    "guidance_scale": 2.5,
    "num_images": 1,
    "seed": -1,
    "output_format": "jpeg",
    "enable_base64_output": false,
    "enable_sync_mode": false
}
)

print(output["outputs"][0])  # → URL of the generated output

Flux Kontext Dev API — Frequently asked questions

What is the Flux Kontext Dev API?

Flux Kontext Dev is a WaveSpeedAI model for image editing, exposed as a REST API on WaveSpeedAI. FLUX.1 Kontext Dev is an open-weight, open-code image-to-image model that edits images from text prompts for precise, text-guided retouching and style transfer. Ready-to-use REST inference API, best performance, no coldstarts, affordable pricing. You can call it programmatically or try it from the playground above.

How do I call the Flux Kontext Dev API?

POST your input parameters to the model's REST endpoint (shown in the API tab of this playground) with your WaveSpeedAI API key in the Authorization header. Submission returns a prediction ID; poll the prediction endpoint until status flips to "completed", then read the output URL from the result. The playground generates a ready-to-paste code sample in Python, JavaScript, or cURL for whatever inputs you've set. Full request/response shape is documented at https://wavespeed.ai/docs/docs-api/wavespeed-ai/flux-kontext-dev.

How much does Flux Kontext Dev cost per run?

Flux Kontext Dev starts at $0.025 per run. That figure is the base price — the final charge scales with the parameters you set in the form (output size, length, count, references, or whatever knobs this model exposes), so a higher-quality or larger output costs more than a minimal one. The exact cost for your current input is shown live next to the Generate button before you submit, and the actual per-call charge is recorded on the prediction afterwards.

What inputs does Flux Kontext Dev accept?

Key inputs: `prompt`, `image`, `size`, `seed`, `guidance_scale`, `num_inference_steps`. The full JSON schema (types, defaults, allowed values) is rendered above the Generate button and mirrored in the API reference at https://wavespeed.ai/docs/docs-api/wavespeed-ai/flux-kontext-dev.

How long does Flux Kontext Dev take to generate?

Average end-to-end generation time on WaveSpeedAI is around 8 seconds per request — measured across recent runs. Queue time scales with global demand; live status is visible in the prediction record.

Can I use Flux Kontext Dev outputs commercially?

Commercial usage rights depend on the model's license, set by its provider (WaveSpeedAI). The license summary appears on the model card above; see WaveSpeedAI's Terms of Service for platform-level conditions.

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