RemBG Background Removal API – Developer Docs & Integration Guide

Installation of rembg.js


npm i @remove-background-ai/rembg.js

API Reference for rembg.js

@remove-background-ai/rembg.js is a zero-config Node.js wrapper for the free Rembg API, enabling background removal with simple, customizable parameters.

Parameters for RemBG.js

Parameter	Type	Required	Default	Description
apiKey	string	Required	–	Your Rembg API key
inputImage	string \| Buffer \| { base64: string }	Required	–	Image file, buffer, or base64 payload
onDownloadProgress	(event) => void	Optional	–	Hook for upload progress events
onUploadProgress	(event) => void	Optional	–	Hook for download progress events
options.format	webp (default) \| png	Optional	webp	Specifies the output image format. Either "webp" (default) or "png"
options.returnBase64	boolean	Optional	false	Return Base64 string instead of file
options.returnMask	boolean	Optional	false	Return only the alpha mask
options.w	number	Optional	–	Target width (maintains aspect ratio)
options.h	number	Optional	–	Target height (maintains aspect ratio)
options.exact_resize	boolean	Optional	false	Force exact width × height (may distort)
options.angle	number	Optional	0	Rotation angle in degrees
options.expand	boolean	Optional	true	Add padding so rotated images aren’t cropped
options.bg_color	string	Optional	-	Optional solid background color in hex (e.g. #FFFFFFFF) or named color (e.g. "red", "blue")

Setting up Your Environment: Ensure you have a .env file in your project root containing your API key.
Importing the Necessary Modules: Begin by importing the rembg function from @remove-background-ai/rembg.js and the dotenv module to handle environment variables.
Configuring Progress Callbacks: The library offers onDownloadProgress and onUploadProgress callbacks to track the progress of file operations. In the provided example, we're logging these events directly to the console.

Now, let's take a closer look at a sample usage:


// script.mjs file

import  { rembg } from '@remove-background-ai/rembg.js';
import dotenv from 'dotenv';
// Load environment variables from .env file
dotenv.config();

// API_KEY will be loaded from the .env file
const API_KEY = process.env.API_KEY;

// log upload and download progress
const onDownloadProgress = console.log;
const onUploadProgress = console.log;
rembg({
    apiKey: API_KEY,
    inputImage: './input.png', //inputImage can be one of these: string | Buffer | { base64: string };
    onDownloadProgress,
    onUploadProgress
}).then(({ outputImagePath, cleanup }) => {
    console.log('✅🎉 background removed and saved under path=', outputImagePath);
    // if called, it will cleanup (remove from disk) your removed background image
    // cleanup();
});

Remember, the cleanup function can be called if you wish to remove the processed image from your disk after background removal.

Showing Progress bar

When integrating a background removal service, it's often beneficial to provide users with feedback on the progress of their upload or download request. To facilitate this, you can define your own onDownloadProgress and onUploadProgress callbacks. Both of these callbacks accept AxiosProgressEvent as an event parameter. As the request proceeds, these callbacks are invoked multiple times, allowing you to, for instance, display a progress bar and adjust its length based on the progress.


 (base) root@DESKTOP-C0Q8KK7:~/rembg.js-test# node index.mjs
 {
   loaded: 65687,
   total: 68474,
   progress: 0.9592984198381868, <---- @95% progress 
   bytes: 65687,
   rate: undefined,
   estimated: undefined,
   upload: true  <---- upload progress
 }
 {
   loaded: 68474,
   total: 68474,
   progress: 1, <---- @100% progress 
   bytes: 2787,
   rate: undefined,
   estimated: undefined,
   upload: true <---- upload progress 
 }
 {
   loaded: 1002,
   total: 68824,
   progress: 0.014558874811112402, <---- @1% progress 
   bytes: 1002,
   rate: undefined,
   estimated: undefined,
   download: true <---- download progress 
 }
 {
   loaded: 68824,
   total: 68824,
   progress: 1, <---- @100% progress 
   bytes: 67822,
   rate: undefined,
   estimated: undefined,
   download: true <---- download progress
 }
 ✅🎉 background removed and saved under path=/tmp/rembg--3339-DBqqeJ2eOs4D-.png

Curl


# Full example: upload an image and remove its background with all optional parameters
curl -X POST "https://api.rembg.com/rmbg"
  -H "x-api-key: YOUR_API_KEY_HERE"          # your personal API key
  -F "image=@/path/to/image.jpg"             # input image file
  -F "format=webp"                           # output format: webp (default) or png
  -F "w=800"                                 # target width in pixels (maintains aspect ratio unless exact_resize=true)
  -F "h=600"                                 # target height in pixels
  -F "exact_resize=false"                    # true = force exact w × h, may distort
  -F "mask=false"                            # true = return only the alpha mask instead of full image
  -F "bg_color=#ffffffff"                    # optional solid background color (RGBA hex)
  -F "angle=0"                               # rotate the image by given degrees after processing
  -F "expand=true"                           # add padding so rotated images don’t get cropped

HTTP


POST /rmbg HTTP/1.1
Host: api.rembg.com
x-api-key: YOUR_API_KEY_HERE
Content-Type: multipart/form-data; boundary=----BOUNDARY

------BOUNDARY
Content-Disposition: form-data; name="image"; filename="image.jpg"
Content-Type: image/jpeg
<binary data of your image goes here>
------BOUNDARY
Content-Disposition: form-data; name="format"
webp
------BOUNDARY
Content-Disposition: form-data; name="w"
800
------BOUNDARY
Content-Disposition: form-data; name="h"
600
------BOUNDARY
Content-Disposition: form-data; name="exact_resize"
false
------BOUNDARY
Content-Disposition: form-data; name="mask"
false
------BOUNDARY
Content-Disposition: form-data; name="bg_color"
#ffffffff
------BOUNDARY
Content-Disposition: form-data; name="angle"
0
------BOUNDARY
Content-Disposition: form-data; name="expand"
true
------BOUNDARY--

Python Requests


import requests

# Endpoint URL for the background-removal API
url = "https://api.rembg.com/rmbg"

# Required API key header
headers = {
    "x-api-key": "YOUR_API_KEY_HERE"
}

# The image file to process (opened in binary mode)
files = {
    "image": open("/path/to/image.jpg", "rb")
}

# Optional form fields supported by your backend.
# Adjust values as needed; any of these can be omitted.
data = {
    "format": "webp",         # Output format: "webp" (default) or "png"
    "w": 800,                 # Target width (maintains aspect ratio unless exact_resize is true)
    "h": 600,                 # Target height
    "exact_resize": "false",  # "true" forces exact w×h, may distort
    "mask": "false",          # "true" returns only the alpha mask
    "bg_color": "#ffffffff",  # Optional solid background color (RGBA hex)
    "angle": 0,               # Rotation angle in degrees
    "expand": "true",         # Add padding so rotated images aren’t cropped
}

# Send the POST request with headers, file, and extra form data
response = requests.post(url, headers=headers, files=files, data=data)

# Handle the response
if response.status_code == 200:
    # Save the processed image to disk
    with open("output.webp", "wb") as f:
        f.write(response.content)
    print("Background removed successfully → saved as output.webp")
else:
    # Print error details if the request failed
    print("Error:", response.status_code, response.text)

Membership & Credits Usage

Check your membership tier, credit balance, and usage (app + API) for a given month. Authenticate with your API key.

Endpoint

GET https://www.rembg.com/api/membership-usage

Authentication

Send your API key in the x-api-key header: x-api-key: YOUR_API_KEY_HERE

Query parameters (optional)

Parameter	Type	Description
year	number	Year (e.g. 2026). Defaults to current year if omitted.
month	number (1–12)	Month (1–12). Defaults to current month if omitted.

cURL example

curl --location 'https://www.rembg.com/api/membership-usage?year=2026&month=1' \
  --header 'x-api-key: YOUR_API_KEY_HERE'

Response

{
  "membership": "Premium-20000",
  "credits": 18500,
  "prepaidCredits": 2000,
  "app_usage": 8500,
  "api_usage": 10000
}

Error Responses

All error responses return a JSON body with a status field matching the HTTP status code.

Single Error Response

HTTP/1.1 400 Bad Request

HTTP/1.1 400 Bad Request
Content-Type: application/json

{
  "error": "Image width (12000px) exceeds the maximum allowed width of 10000px.",
  "field": "image",
  "status": 400
}

Multiple Validation Errors Response