"To that end, today we are releasing a list of DOH requirements, available on the Mozilla wiki, that we will use to vet potential resolvers for Firefox. The requirements focus on three areas: 1) limiting data collection and retention from the resolver, 2) ensuring transparency for any data retention that does occur, and <i>3) limiting any potential use of the resolver to block access or modify content.</i>"<p>I sometimes use a local resolver bound to localhost that blocks ads by pointing to a custom root.<p>If someone aiming to be on the TRR list sets up a remote resolver that blocks ads (or replaces them with blank images) perhaps using the same technique, it could allow Firefox users to get ad blocking by default, by using DOH.<p>I wonder if that would violate Mozilla's requirements?<p>Are ads considered "content"?<p>There is of course precedent for blocking undesirable content via DNS as a "service".<p>Third party DNS service, for example the famous one that starts with "O", has been used to block certain content, e,g, at schools.<p>This was offered as a fee-based service.<p>If I remember correctly they also offered "free" service which was subject to redirection of NXDOMAIN to paid placement "search" results/ads.