We present three scenarios that demonstrate how Cross-Origin Resource Sharing works. All these examples use {{domxref("XMLHttpRequest")}}, which can make cross-site requests in any supporting browser.
-A discussion of Cross-Origin Resource Sharing from a server perspective (including PHP code snippets) can be found in the Server-Side Access Control (CORS) article.
-Some requests don’t trigger a CORS preflight. Those are called “simple requests” in this article, though the {{SpecName('Fetch')}} spec (which defines CORS) doesn’t use that term. A “simple request” is one that meets all the following conditions: