Instasize API

Authentication

Create a key in your account and send it on every request, either as an x-api-key header or as a bearer token in Authorization. Keys are shown once when created; store them in an environment variable, never in client-side code.

x-api-key: isk_live_...
# or
Authorization: Bearer isk_live_...

• isk_test_ — sandbox. Free, 1,000 successful calls per calendar month per account (all your sandbox keys share it), output carries an Instasize watermark.
• isk_live_— live. Clean output, billed to the AI credits on the key owner's plan.

Remove background

POST /remove-background. Send the image as multipart image or as JSON { "image_url": "..." }. Returns a PNG with a transparent background. 1 credit.

curl -X POST https://instasize.com/api/v1/remove-background \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -F image=@photo.jpg \
  -o cutout.png

Resize

POST /resize. Pass a preset such as instagram/story, explicit width and height, or a presets array to get several sizes in one call. A single output returns the image bytes; multiple outputs return JSON with one URL per preset. 1 credit per output.

By preset

curl -X POST https://instasize.com/api/v1/resize \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -F image=@photo.jpg \
  -F preset=instagram/story \
  -o story.jpg

Many presets at once (JSON)

curl -X POST https://instasize.com/api/v1/resize \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"image_url":"https://example.com/photo.jpg","presets":["instagram/story","instagram/square","tiktok/video-post"]}'

Presets

GET /presets lists every platform and size the resize endpoint accepts, as platform/name ids with pixel dimensions. No key required.

curl https://instasize.com/api/v1/presets

AI expand

POST /expand. Grows the canvas and paints the new area to continue the scene. Say how much to add with left, right, top and bottom (pixels), or give an aspect such as 1:1 or a preset id and the padding is worked out for you, centred, never cropping the source. Every side rounds up to a multiple of 64 and stops at 2000 px; the response says what was actually added. Optional prompt, negative_prompt and seed. Output is the worker's ~1024 px render. 5 credits.

By aspect ratio

curl -X POST https://instasize.com/api/v1/expand \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -F image=@photo.jpg \
  -F aspect=1:1 \
  -F prompt="sandy beach, soft evening light" \
  -o expanded.jpg

By pixels per side (JSON in, JSON out)

curl -X POST "https://instasize.com/api/v1/expand?response=json" \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"image_url":"https://example.com/photo.jpg","left":256,"right":256}'

{
  "image": "data:image/jpeg;base64,...",
  "width": 1024,
  "height": 1024,
  "format": "jpeg",
  "added": { "left": 0, "right": 0, "top": 192, "bottom": 192 },
  "credits_charged": 5,
  "sandbox": false
}

AI upscale

POST /upscale. Send the image and nothing else; the model enlarges and sharpens it and returns the image (PNG when the worker keeps transparency, otherwise JPEG). Add ?response=json to get a data URL together with the source size. 5 credits.

curl -X POST https://instasize.com/api/v1/upscale \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -F image=@photo.jpg \
  -o upscaled.jpg

AI object removal

POST /remove-object. Two images: the image and a mask of exactly the same pixel size, white where the object is and black everywhere else. Both travel the same way — multipart files, JSON data URLs, or image_url and mask_url. A mask of a different size is refused with 400 invalid_request. Returns PNG when the result has transparency, otherwise JPEG. 5 credits.

curl -X POST https://instasize.com/api/v1/remove-object \
  -H "x-api-key: $INSTASIZE_API_KEY" \
  -F image=@photo.jpg \
  -F mask=@mask.png \
  -o object-removed.jpg

Errors

Every non-2xx response uses one envelope. Quote the request_id when you write in; it is also returned on successful calls as the X-Request-Id header.

{
  "error": {
    "code": "usage_exceeded",
    "message": "Sandbox limit reached: 1,000 successful calls per calendar month across all your sandbox keys.",
    "request_id": "req_01J8ZK3M2Q4X"
  }
}

Rate limits

Limits are per key, per minute: sandbox keys 20 requests, live keys 120. Every response carries X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset (seconds until the window resets). Over the limit you get 429 rate_limited; back off until the reset time.

Credits

• Utility, 1 credit: resize per output image (three presets in one call cost 3 credits) and remove-background.
• Generative, 5 credits per call: expand, upscale and remove-object. These run on GPU workers and take longer — allow up to a minute.
• Failed calls (any 4xx or 5xx) are not charged; a charge taken before a failure is refunded.
• Sandbox keys are never billed. Your account gets 1,000 successful sandbox calls per calendar month across all its sandbox keys; refused requests (4xx) do not count.

Live keys spend the same AI credits as the editor, so usage shows in your account next to your keys.

OpenAPI

The machine-readable contract for every endpoint above is at /api/v1/openapi.json. Point a client generator at it, or import it into Postman or Insomnia.