DuckDuckGo offers cross app tracker protection as a feature in their web browser. From what I understand it sets up a local VPN, routes all connection through it and blocks all attempts to access information outside the app? Does Mullvad VPN’s DNS content filter for tracks emulate the exact same thing? Or is there a difference in how these features function?
The results may differ slightly due to different tracker blocklists being used, but both have similar goals. However, they differ in implementation. App Tracking Protection works completely on-device, with the pseudo-VPN preventing all tracking traffic from leaving your device based on local blocklists while letting all other traffic through without routing it anywhere different like a traditional VPN would. DNS blocklists function by responding to your device’s request to find a blocked server with a null address (i.e. “hey DNS server, where do I find this ad/tracker website?” “Oh I don’t know, sorry!”), so while the requests for these ads and trackers leave your device, they don’t get a valid response, meaning the trackers fail to load. This means that while DuckDuckGo doesn’t see your web requests with App Tracking Protection, a blocking DNS server would, though this is already the case when you use Mullvad VPN. The switches simply change your DNS server from Mullvad’s standard DNS resolver to another DNS server hosted by Mullvad that is configured with some ad/tracker blocklists, meaning you still only have to trust Mullvad.