Mastering ArcGIS Server Development with JavaScript

A note on proxies

If you've worked with the ArcGIS JavaScript API for any length of time, or had to support older browsers like Internet Explorer 9 or less, then you've probably come across proxies. Proxies are server-side applications that make web requests on behalf of the web browser, often transmitting and receiving data the browser could not collect on its own. There are three primary reasons why a browser would require a proxy to communicate with a server. They are as follows:

1. The browser is an older browser that does not support Cross Origin Resource Sharing (CORS), and the server requests will be made to a different server from the one the application sits on.
2. The proxy provides additional security keys to access specific data, which might ...