noreferrer

Noreferrer is a value for the rel attribute in HTML that indicates how a link should be treated by the browser when navigating to the linked resource. Specifically, it requests that the browser omit the HTTP Referer header in the request to the destination. In addition, in many browsers the destination page cannot access the originating window via window.opener, reducing the ability of the new page to interact with the source page.

This combination is primarily a privacy and security measure. By not sending the referer, the source URL and any potentially sensitive context are not disclosed to the target site. The potential security benefit includes reducing the risk of tab-nabbing, where the new page could manipulate the original page through window.opener.

Usage and scope: noreferrer is commonly applied to anchor elements (a) that link to external sites. It is often used in combination with noopener, as rel="noopener noreferrer", to ensure both no opener access and no referrer leakage across modern browsers. Some developers also rely on the broader referrer policy mechanisms to control referer behavior sitewide.

Compatibility and notes: rel="noreferrer" is supported by all major modern browsers. While it prevents sending the Referer header for navigation, it does not guarantee anonymity in all contexts (for example, analytics can still be affected by other data, and not all requests are covered by this attribute). It is separate from, but complementary to, the Referrer-Policy header or meta tag, which provides broader and more configurable control over referer information in various contexts.