Yeah when my DNS went sporty I noticed Firefox got very slow to load even local ips and investigated.
Turns out it does two dozen queries on every start. Mostly to unknown Mozilla services but also a few from Google and others I couldn't identify (IP on either AWS or CloudFlare, likely just more Mozilla). And when it can't resolve those hosts it seems to continually retry every few seconds...
Before the apologists arrive, try it yourself. Disable all your add-ons and set your homepage to blank, close Firefox, start wireshark, start Firefox and watch the avalanche.
Turns out it does two dozen queries on every start. Mostly to unknown Mozilla services but also a few from Google and others I couldn't identify (IP on either AWS or CloudFlare, likely just more Mozilla). And when it can't resolve those hosts it seems to continually retry every few seconds...
Before the apologists arrive, try it yourself. Disable all your add-ons and set your homepage to blank, close Firefox, start wireshark, start Firefox and watch the avalanche.