Websites don’t need you to fill out anything to know your OS. Your browser sends a small identifier every time you load a page, and the operating system is part of it. That’s where those usage numbers come from.
And yes, that can be changed. Privacy setups like Whonix, Tor Browser, hardened browsers like LibreWolf, or running them inside isolated VMs on QubesOS can all limit or standardize what gets reported.
From Tor support:
“The User-Agent string is a value websites can use to identify details about your browser, operating system (OS), CPU architecture, vendor, and version. …
All Windows appear as Windows 10. All macOS appear as OS X 10.15. All Android as Android 10. All other systems like all Linux distributions (including Tails and Qubes), *BSD and other operating systems are grouped together and reported as ‘Linux running X11’.”
https://support.torproject.org/tor-browser/features/fingerprinting-protections/?utm_source=chatgpt.com
As long as you don’t modify things that leak extra details, sites mostly see whatever that browser chooses to tell them. These stats mainly reflect default, non-privacy setups.
