Tracker/analytics data won't be correct for Firefox or people using privacy-centric browsers as they inherently block that. I think it'd be hard to get a real number without polling a lot of people.
A lot of people assume Chrome has the monopoly based on looking at false analytics.
Firefox definitely sends its user-agent to servers, so wouldn't server-side analytics still work?
Perhaps, and this is likely the case with most users. But there still exists many users with extensions disabling fingerprinting and such.
Theoretically, server-side analytics could use the user-agent strings and other headers in the request to have infallible analytics. In practice, a lot of server-side analytics in practice rely on third-party tracking scripts (like Google Analytics) and other such practices that get blocked by tools like Privacy Badger, etc.
I wish Cloudflare would publish stats based on user agents. They must have a good idea about the real numbers
What do you want to know?
What percentage of traffic comes from Firefox.
Thankfully the new Microsoft Edge will save us. /s