Firefox telemetry is opt-out on the Nightly, DevEdition, and Beta channels, but (mostly) opt-in on the Release channel. The opt-in telemetry from the Release channel has limited use because it is not representative of all users.
Here is a list of Firefox's telemetry measurements. Those that are opt-out on the Release channel are tagged "releaseChannelCollection": "opt-out". Adding a new opt-out measurement requires an additional privacy review.
Firefox telemetry is opt-out on the Nightly, DevEdition, and Beta channels, but (mostly) opt-in on the Release channel. The opt-in telemetry from the Release channel has limited use because it is not representative of all users.
Here is a list of Firefox's telemetry measurements. Those that are opt-out on the Release channel are tagged "releaseChannelCollection": "opt-out". Adding a new opt-out measurement requires an additional privacy review.
https://hg.mozilla.org/mozilla-central/file/tip/toolkit/comp...