HTTP CORS definition

Mozilla CORS definition

Cross-Origin Resource Sharing (CORS) is a mechanism that uses additional HTTP headers to tell a browser to let a web application running at one origin (domain) have permission to access selected resources from a server at a different origin.

A web application executes a cross-origin HTTP request when it requests a resource that has a different origin (domain, protocol, and port) than its own origin.

An example of a cross-origin request: The frontend JavaScript code for a web application served from uses XMLHttpRequest to make a request for .