The server possibly can send back a 406 (Not Acceptable) error code when unable to serve content in a matching language. However, such a behavior is rarely implemented for a better user experience, and servers often ignore the Accept-Language header in such cases.

// Download a json but don't reveal who is downloading it fetch("sneaky.json", {referrerPolicy: "no-referrer"}) .then(function(response) { /* consume the response */ }); // Download a json but pretend another page is downloading it fetch("sneaky.json", {referrer: "https://example.site/fake.html"}) .then(function(response) { /* consume the response */ }); // You can only set same-origin referrers. fetch("sneaky.json", {referrer: "https://cross.origin/page.html"}) .catch(function(exc) { // exc.name == "TypeError" // exc.message == "Referrer URL https://cross.origin/page.html cannot be cross-origin to the entry settings object (https://example.site)." }); // Download a potentially cross-origin json and don't reveal // the full referrer URL across origins fetch(jsonURL, {referrerPolicy: "origin-when-cross-origin"}) .then(function(response) { /* consume the response */ }); // Download a potentially cross-origin json and reveal a // fake referrer URL on your own origin only. fetch(jsonURL, {referrer: "https://example.site/fake.html", referrerPolicy: "origin-when-cross-origin"}) .then(function(response) { /* consume the response */ });