Disclosure: I don't have any relation to Mozilla (so some of this could be wrong), and about half of it I discovered after reading this comment. I do run Firef

Disclosure: I don't have any relation to Mozilla (so some of this could be wrong), and about half of it I discovered after reading this comment. I do run Firefox Nightly, and follow Firefox development somewhat. I don't see the same screen you do (perhaps something to do with telemetry being force-enabled in nightly?) so this is based off of what you wrote: > Is this a study... Studies are generally minor tweaks in user configuration sent to a subset of users (often nightly), and then telemetry between control and experiment groups is compared. You can see what studies you have been in at about:studies. For example, some of mine include setting the user-agent to Firefox 100 (to test a 3-digit number), enabling fission (and a number of things with process counts and whatnot), enabling HTTP/3, and (I kid not) "Changing a pref that does nothing - to check enrollment and unenrollment reliability." A lot of the time if you inspect element the source has a bug number you can look at (which really ought to be a built-in feature). > The result of crash logging You can see this in about:crashes; this is when the browser or a process (eg. GPU) crashes. > Data about your interactions with Firefox Probably, this seems like the most broad and undefined one > Number and type of installed addons Seems self-explanatory > Firefox features offered by Mozilla or our partners Not really sure about this one, presumably it relates more to things that have to do with third-parties or them making money > Overview of tracking See about:telemetry. That has links to a number of other pages I didn't realize existed before today, but which seem to have a pretty comprehensive public overview.