[Setting Up DoH In Firefox]
DoH (DNS-over-HTTPS) is a protocol where all the DNS requests a computer sends off is encrypted with HTTPS. This means that your network administrator or ISP can't see what websites you're accessing. This blog post is about setting it up on Firefox desktop and Firefox Android.
Choose a DNS server, there are a few listed on Privacytools.io. For your own privacy, it is best practice to choose a service outside of The Fourteen Eyes.
In Firefox go to Preferences and in General scroll all the way down to Network Settings, click on Settings and check Enable DNS over HTTPS
Now you can leave the provider on Cloudflare but for privacy concerns I would highly encourage you to change it to a DNS server you trust. Select Custom as provider and enter the DNS server you chose.
Congratulations! You have set up DNS over HTTPS.
Now setting up DoH on Firefox for Android is a just a little more involved than on Firefox desktop, but it isn't too bad.
As with Desktop Firefox you will need to choose a DNS server (or you can leave it on Cloudflare, but I would advice against it).
Open a new tab on Firefox and go to about:config, you will see a list with a bunch of settings.
Type in the search bar network.ttr.mode, click on it and change the number to 2.
If you're going to use Cloudflare, you're done. If you chose another DNS server, Continue on with step 4
Type in the search bar network.trr.uri, click on it and change the value to the DNS server you'd like to use.
Repeat step 4 for network.trr.custom_uri
Great! Now you've set up DoH on Firefox for Android.
To see if you set everything up correctly, you can perform a standard test over at DNSLeaktest.com.