Migrate from Stability AI API to Railwail

TL;DR — Switch in Under 10 Minutes

• Drop multipart/form-data uploads to api.stability.ai — use the OpenAI images.generate API
• Stable Diffusion 3.5 Large, Medium, SDXL, Stable Image Ultra, Stable Video all available
• Standard JSON request body instead of form-data
• EU-hosted endpoint, EUR billing
• Plus access to Flux, DALL-E 3, GPT-4o, Claude on the same key

Why Move Off Stability AI Platform?

Stability's REST API for SD 3.5 and Stable Image works but uses multipart/form-data and a custom credit accounting scheme that does not match the rest of your AI stack. Railwail exposes the same models behind the OpenAI Chat / Images API with simple JSON requests and per-call pricing.

Step 1 — Get a Railwail API Key

Sign up at railwail.com and generate a key.

Step 2 — Replace form-data with JSON

TypeScript / JavaScript

Before (Stability):

const form = new FormData();
form.append("prompt", "a cyberpunk city at sunset");
form.append("output_format", "webp");
form.append("aspect_ratio", "16:9");

const res = await fetch("https://api.stability.ai/v2beta/stable-image/generate/sd3", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.STABILITY_API_KEY}`,
    Accept: "image/*",
  },
  body: form,
});
const buf = Buffer.from(await res.arrayBuffer());

import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://api.railwail.com/v1",
});

const res = await client.images.generate({
  model: "stable-diffusion-3.5-large",
  prompt: "a cyberpunk city at sunset",
  size: "1792x1024",
  response_format: "url",
});
console.log(res.data[0].url);

Python

from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://api.railwail.com/v1",
)

resp = client.images.generate(
    model="stable-diffusion-3.5-large",
    prompt="a cyberpunk city at sunset",
    size="1792x1024",
)
print(resp.data[0].url)

cURL

curl https://api.railwail.com/v1/images/generations \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "stable-diffusion-3.5-large",
    "prompt": "a cyberpunk city at sunset",
    "size": "1792x1024"
  }'

API Endpoint Mapping

Model Mapping

Pricing Comparison (per image, May 2026)

Why Railwail Over Stability AI Direct

• EU hosting and EUR billing
• Simple JSON requests instead of multipart/form-data
• Standard OpenAI images.generate / images.edits API
• Adds Flux Pro, DALL-E 3 — Stability has only Stable Diffusion family
• Same per-image pricing
• Built-in playground for prompt iteration

FAQ

Are inpaint and outpaint supported?

Yes. Use POST /v1/images/edits with a base image and mask. Pass mode: 'inpaint' or 'outpaint' as an extension parameter.

What about ControlNet (sketch, structure, depth)?

ControlNet modes are accessible via POST /v1/images/edits with mode: 'sketch', 'structure', 'depth' and the appropriate control_image.

Can I do batch generation?

Yes. Pass n: 4 in the request to get 4 images in one call. Pricing scales linearly per image.

Is the negative_prompt supported?

Yes. Pass negative_prompt as an extension parameter.

What about Stable Audio?

Stable Audio 2.0 is available as stable-audio-2-0 via POST /v1/audio/generations (text-to-music).

Next Steps

• Sign up at railwail.com
• Generate an API key
• Replace multipart/form-data calls with the OpenAI images SDK
• Use stable-diffusion-3.5-large etc. as model IDs
• Read the reference at railwail.com/docs
• Compare pricing at railwail.com/pricing