Firefox bypassing Pi-Hole even after setting Firefox network.trr.mode to "5"

[Gewehr98]

Please follow the below template, it will help us to help you!

Expected Behaviour:

I knew Firefox browser was implementing DOH, but from all discussions it would be a simple task of disabling DOH via the network.trr.mode settings, so I set those to "5" (OFF)

Actual Behaviour:

Firefox still pulls all sorts of ads that do not show up in the PiHole query logs. I do a IPCONFIG /FLUSHDNS in a command box, and that works for just a minute or two.

I understand there is an upstream Canary resolver that Firefox is using, should I do something with that address? This is pretty much defeating the ad blocking that my PiHole used to do when using Firefox/Waterfox.

[jfb]

@Gewehr98

I understand there is an upstream Canary resolver that Firefox is using, should I do something with that address?

No. This is already handled with Pi-hole, but it is only effective if the DoH setting in Firefox is enabled by default. If you have toggled it off and then back on, the canary domain will have no effect, since you have made a deliberate decision to use DoH.

Add use-application-dns.net = NXDOMAIN in ProcessDNSSettings rather t…

Configuring Networks to Disable DNS over HTTPS | Firefox Help

@Gewehr98

Firefox still pulls all sorts of ads that do not show up in the PiHole query logs

After you have eliminated DoH as a problem, ensure the host OS running on that client is using Pi-hole (and only Pi-hole for DNS):

Why should Pi-hole be my only DNS server?

Reduced Ad Blocking Capability The main reason you should Pi-hole as your only DNS server is that you will see increased performance in the blocking of ads. If you have two DNS servers (Pi-hole and something else), your network clients may not always query Pi-hole for name resolution. If a query happens to be answered from a non-Pi-hole DNS server, your block lists will not apply (since that DNS server doesn't know about them). All Queries Need To Go Through Pi-hole First Since other DNS se…

[Gewehr98]

No joy to date. My Pi-Hole is my entire home network's DNS server, and since Day 1 of Pi-Hole installation here has always been set as such via my router's DNS settings. It's only been since Firefox (and perhaps Waterfox) went to DoH that I've seen this problem. Disabling it in the browser settings itself has not stopped Firefox from circumventing the PiHole. I understand that Google Chrome and Microsoft Edge will also being using DoH in the not-so-distant future? My Pi-Holes query log shows that it is blocking some locations, but Firefox appears to be letting GoogleAdSense traffic through.