You can actually see all of the telemetry data Firefox is sending by going to about:telemetry in your browser.
You can also see all of the probes it could be collecting here: https://probes.telemetry.mozilla.org/
Keep in mind that the telemetry that is captured in Firefox goes through a thorough review process, so that it respects user privacy: https://wiki.mozilla.org/Data_Collection
Even with all telemetry disabled (including the option "Allow Firefox to send technical and interaction data to Mozilla") and without anything showing on that page, the browser still sends out interaction data by means of so called "pings", URL parameters, etc.
Wow, a browser is making network connections, how dare it. Come on, these things are there so that if you are on "connected" to a network that require some registration, e.g. an airport, then you can actually be forwarded to that registration page.
Like what do you even think, Mozilla people are sitting on top of all that sweet
PING www.mozilla.org (3.161.119.172) 56(84) bytes of data.
64 bytes from server-3-161-119-172.vie50.r.cloudfront.net (3.161.119.172): icmp_seq=1 ttl=248 time=4.06 ms
64 bytes from server-3-161-119-172.vie50.r.cloudfront.net (3.161.119.172): icmp_seq=2 ttl=248 time=4.16 ms
64 bytes from server-3-161-119-172.vie50.r.cloudfront.net (3.161.119.172): icmp_seq=3 ttl=248 time=3.64 ms
It makes these connections even when all the things mentioned in the official "How to stop Firefox from making automatic connections"[1] are disabled. This includes the captive portal detection you allude to.
Regardless:
The browser asks me if I allow it to make these connections.
I tell it in unmistakable and irrevocable terms that I do not.
The browser makes these connections anyway.
The problem was never the connections or the contents of the data stream. You were aware of this before posting your comment, and yet you commented anyway. You are a troll.
Am I really the troll, or those who bring down the only remaining truly libre, open-source browser engine over stupid nitpicky bullshits, while not contributing anything positive to improve on the status?
The point is, if you provide an option to turn off telemetry, it should be off. No exception. In this case of an airport connection requiring a registration page intranetwork, this occurs via first request through their proxy with header redirect.
The point is, don’t lie about saying you respect privacy with half-baked options and telemetry for me but not for thee bs. If I turn off telemetry, you aren’t allowed to send telemetry. Of any kind. Not a crash log. Not an install token. Not a call home to see if maybe possibly your on an airport wifi and make-our-app-work-edge-case()
There is a distinct difference between telemetry and the captive portal requests Firefox makes. The captive portal checks have nothing to do with telemetry and contain no payload, which is why they are not covered by that setting.
Even with all telemetry disabled (including the option "Allow Firefox to send technical and interaction data to Mozilla") and without anything showing on that page, the browser still sends out interaction data by means of so called "pings", URL parameters, etc.