can I upgrade my iMAC OS High Sierra 10.13.6 late 2009 to a later OS
From Identify your iMac model - Apple Support, a 2009 iMac supports macOS High Sierra as the highest version.
From Identify your iMac model - Apple Support, a 2009 iMac supports macOS High Sierra as the highest version.
I'm disappointed that I am unable to upgrade the OS. To a later version, I don't see why I should be expected to purchase a new computer.
The computer is in perfect condition and I still have 999gb of free space left
The hardware in your computer is almost thirteen years old. Much has changed in the span of the past decade.
No computer manufacturer is going to spend resources (money) trying to support old technology. That's just the way it is.
Thirteen years is a very good run for a computer from any maker.
You don't have to buy a new computer, but don't expect any further support from Apple for your old Mac.
The world turns, my friend.
If you need to run a higher version of macOS, you may want to consider a Virtualization engine running on 10.13.6, which can let you run Big Sur or older versions.
For example the free VirtualBox can run - https://www.virtualbox.org/wiki/Guest_OSes.
I am glad to see your iMac has been a steady workhorse.
Upgrade High Sierra 10.13.6
