How to use Cors anywhere to reverse proxy and add CORS headers

I've been reading for two hours the documentation of this Reverse proxy to add CORS headers, and I'm not able to use. Can you please help with a simple example how to use that.


I've tried that example in a javascript

(function() {
var cors_api_host = '';
var cors_api_url = 'https://' + cors_api_host + '/';
var slice = [].slice;
var origin = window.location.protocol + '//' +;
var open =; = function() {
    var args =;
    var targetOrigin = /^https?:\/\/([^\/]+)/i.exec(args[1]);
    if (targetOrigin && targetOrigin[0].toLowerCase() !== origin &&
        targetOrigin[1] !== cors_api_host) {
        args[1] = cors_api_url + args[1];
    return open.apply(this, args);

I don't understand really if I need node.js or what exactly



CORS Anywhere helps with accessing data from other websites that is normally forbidden by the same origin policy of web browsers. This is done by proxying requests to these sites via a server (written in Node.js, in this case).

"To use the API, just prefix the URL with the API URL.". That's really all of it. So, instead of requesting, you will request CORS Anywhere will then make the request on behalf of your application, and add CORS headers to the response so that your web application can process the response.

The snippet from your question automatically modifies the URL for requests generated by XMLHttpRequest if needed. This snippet is not required, you can just prepend the CORS Anywhere API URL yourself, as done in the demo page.

The repository on Github ( contains the source code of the server that powers CORS Anywhere. If you are a front-end dev, then that's all you need to know. If your application has many users, then you should host CORS Anywhere yourself, to avoid eating up all resources on the public CORS Anywhere server.


I defer to Rob, but here is my attempt at an answer to your question.

(Rob, please feel free to correct this answer; and thank you for CORS Anywhere. It recently saved me a heap of trouble.)

  1. Install Node.js.
  2. Install CORS Anywhere.

    For example, at a command prompt, enter:

    npm install cors-anywhere

    (This example command installs CORS Anywhere under the current directory, in node_modules\cors-anywhere.)

  3. Run CORS Anywhere.

    For example, at a command prompt, enter:

    node cors-anywhere.js

CORS Anywhere responds with a message like this:

Running CORS Anywhere on

(The IP address is localhost; your computer.)

You can specify the port in an environment variable, but I chose to edit the value in my local copy of cors-anywhere.js.

Now, suppose you want to use a non-CORS-enabled web service at the following URL:

Instead of using that original URL, you use the CORS Anywhere domain and port, followed by the original URL as the path component:


(You can omit the leading http:// from the original URL.)


You can also check this out:

You can make your own in 3 minutes uploading the code to a free cloudflare worker!


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