When you send a request (like submitting a login form or updating account settings), the browser automatically attaches these headers. A secure server will check them to prevent attacks:
: A user on site-a.com clicks a button that sends a POST to site-b.com . sec,fetch,site:,cross,site
If you are looking for the exact syntax used in a network request, it usually looks like this: When you send a request (like submitting a
: The server sees cross-site on a sensitive POST action and rejects it because it knows this request didn't originate from its own trusted frontend. Summary of the Headers sec,fetch,site:,cross,site
— Indicates the "how" (using the Fetch API/CORS).
: The browser adds sec-fetch-site: cross-site and sec-fetch-mode: navigate (or cors ).