The updns service responds with
NXDOMAIN for filtered domains.
In the following screenshot you see that Snapchat App Analytics is blocked by the updns DoH server.
Our adfree DoH server works best against tracking by mobile apps. DNS-based blocking is very coarse-grained. We therefore recommend you use browsers with blocking extensions and use our DNS service primarily to counter mobile app tracking. You can exclude e.g. your mobile browser from Intra: