credentials

Request: Credentials mode.

Specifies whether user credentials should be sent with the request. The default value is omit, which indicates that user credentials (or any other credentials) should be omitted. Server-side, there are no "default" rules for authorization material present on a request; what you send is what is sent, so this property does nothing.

From MDN: "The credentials read-only property of the Request interface indicates whether the user agent should send or receive cookies from the other domain in the case of cross-origin requests."

See also: MDN, Request.credentials.