It is the desktop where Firefox has a 4% market share right now. Once you consider all traffic it drops down to 2%.
Source: https://gs.statcounter.com/browser-market-share/desktop/worl...
Source: https://gs.statcounter.com/browser-market-share/desktop/worl...
For some reason that part of the story always seems to get omitted, which I find bizarre. But the web pivoted to mobile and Google flexed its monopoly powers. I would argue that upwards of 95% of the change in market share is explained by those two factors.
Looking at the last 10 years gives a different perspective (not great for Firefox but maybe underscores something is different recently in general):
https://gs.statcounter.com/browser-market-share/desktop/worl...