CORS Anywhere is a NodeJS proxy which adds CORS headers to the proxied request.

The url to proxy is literally taken from the path, validated and proxied. The protocol part of the proxied URI is optional, and defaults to "http". If port 443 is specified, the protocol defaults to "https".

This package does not put any restrictions on the http methods or headers, except for cookies. Requesting user credentials is disallowed. The app can be configured to require a header for proxying a request, for example to avoid a direct visit from the browser.

The package also includes a Procfile, to run the app on Heroku. More information about Heroku can be found at https://devcenter.heroku.com/articles/nodejs.

Example

// Heroku defines the environment variable PORT, and requires the binding address to be 0.0.0.0
var host = process.env.PORT ? '0.0.0.0' : '127.0.0.1';
var port = process.env.PORT || 8080;

var cors_proxy = require('cors-anywhere');
cors_proxy.createServer({
    originWhitelist: [], // Allow all origins
    requireHeader: ['origin', 'x-requested-with'],
    removeHeaders: ['cookie', 'cookie2']
}).listen(port, host, function() {
    console.log('Running CORS Anywhere on ' + host + ':' + port);
});

Request examples:

• http://localhost:8080/http://google.com/ - Google.com with CORS headers
• http://localhost:8080/google.com - Same as previous.
• http://localhost:8080/google.com:443 - Proxies https://google.com/
• http://localhost:8080/ - Shows usage text, as defined in libs/help.txt
• http://localhost:8080/favicon.ico - Replies 404 Not found

Live examples:

• https://cors-anywhere.herokuapp.com/
• https://robwu.nl/cors-anywhere.html - This demo shows how to use the API.

Documentation

Client

To use the API, just prefix the URL with the API URL. Take a look at demo.html for an example. A concise summary of the documentation is provided at lib/help.txt.

If you want to automatically enable cross-domain requests when needed, use the following snippet:

(function() {
    var cors_api_host = 'cors-anywhere.herokuapp.com';
    var cors_api_url = 'https://' + cors_api_host + '/';
    var slice = [].slice;
    var origin = window.location.protocol + '//' + window.location.host;
    var open = XMLHttpRequest.prototype.open;
    XMLHttpRequest.prototype.open = function() {
        var args = slice.call(arguments);
        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);
    };
})();

If you're using jQuery, you can also use the following code instead of the previous one:

jQuery.ajaxPrefilter(function(options) {
    if (options.crossDomain && jQuery.support.cors) {
        options.url = 'https://cors-anywhere.herokuapp.com/' + options.url;
    }
});

Server

The module exports createServer(options), which creates a server that handles proxy requests. The following options are supported:

• function getProxyForUrl - If set, specifies which intermediate proxy to use for a given URL. If the return value is void, a direct request is sent. The default implementation is proxy-from-env, which respects the standard proxy environment variables (e.g. https_proxy, no_proxy, etc.).
• array of strings originBlacklist - If set, requests whose origin is listed are blocked.
  Example: ['https://bad.example.com', 'http://bad.example.com']
• array of strings originWhitelist - If set, requests whose origin is not listed are blocked.
  If this list is empty, all origins are allowed. Example: ['https://good.example.com', 'http://good.example.com']
• boolean redirectSameOrigin - If true, requests to URLs from the same origin will not be proxied but redirected. The primary purpose for this option is to save server resources by delegating the request to the client (since same-origin requests should always succeed, even without proxying).
• array of strings requireHeader - If set, the request must include this header or the API will refuse to proxy.
  Recommended if you want to prevent users from using the proxy for normal browsing.
  Example: ['Origin', 'X-Requested-With'].
• array of lowercase strings removeHeaders - Exclude certain headers from being included in the request.
  Example: ["cookie"]
• dictionary of lowercase strings setHeaders - Set headers for the request (overwrites existing ones).
  Example: {"x-powered-by": "CORS Anywhere"}
• string helpFile - Set the help file (shown at the homepage).
  Example: "myCustomHelpText.txt"

For advanced users, the following options are also provided.

• httpProxyOptions - Under the hood, http-proxy is used to proxy requests. Use this option if you really need to pass options to http-proxy. The documentation for these options can be found here.
• httpsOptions - If set, a https.Server will be created. The given options are passed to the https.createServer method.

For even more advanced usage (building upon CORS Anywhere), see the sample code in test/test-examples.js.

License

Copyright (C) 2013 - 2016 Rob Wu rob@robwu.nl

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.