The declarativeNetRequest (DNR) extension API is now available to all extensions starting from Firefox 113, released last week. Extensions with functionality that can be expressed in terms of declarative rules are highly encouraged to transition to the DNR API. Documentation is available at declarativeNetRequest (MDN).

DNR allows extensions to declare rules that describe how the browser should handle network requests. These rules enable Firefox to process network requests without involving the extension further. In comparison with the blocking webRequest API, this offers the following benefits:

• Privacy: Blocking network requests without host permissions. DNR offers more privacy by design because extension code does not get direct access to the request details. Thus request blocking funct