Smart Referer is a security-focused browser extension designed for Firefox that automatically hides HTTP Referer and JavaScript document.referrer for cross-domain requests. This tool is particularly useful for maintaining user privacy while browsing, especially on sites that do not utilize HTTPS. The extension comes with a subscription-based license and is categorized under Security & Privacy, specifically in Anti-Spam & Anti-Spy. It is important to note that Smart Referer has been largely superseded by better browser defaults for HTTPS websites and is no longer actively maintained.

The extension features a whitelist that is regularly updated every 24 hours to prevent potential breakage on rare occasions. Users can view and modify this whitelist, and additional advanced configuration options are available in the repository README file. Smart Referer is also compatible with Waterfox Classic, providing an extra layer of privacy for users who prefer this browser.