What can I do to upgrade my late 2012 iMac?

So......all has been working OK but the last few weeks/months I'm seeing some minor issues, lag, web pages not loading, etc. The spinning beachball has made an appearance too for the first time on this machine...that's always a sad omen ha ha.

Those symptoms strongly suggest your Fusion drive is acting up. Sometimes the mechanical portion of the Fusion goes bad, but it can also slow for other reasons.

Remember we can neither see nor touch your computer in this forum setting. We can guess what is wrong—we are terrible at guessing—but we can give a data-driven eval if you post a system config report. Fortunately there is a safe, secure way to do that without our playing a protracted game of "20 Questions" with you that could go on for days.

We can quickly and within the structural confines of these forums help you determine what issues are at play if you use EtreCheck Pro, available here:

https://etrecheck.com/index

The free version will do nicely for this purpose, although the app is worthy of our financial support.

We can see hard data about drive performance, software issues, and RAM usage. Etrecheck is the development of a long-serving and trusted contributor here expressly for displaying information in these forums to help us help you by remotely evaluating Mac issues. It will not reveal any personal or secure information.

Please see this excellent user tip on how to effectively post long text reports like EtreCheck's into a forum response:

How to use the Add Text Feature When Post… - Apple Community

I believe the report will show that 16GB RAM is adequate. The good thing is the some Fusion slowness issues can be a DIY fix. EtreCheck will tell us.

Yes, yours is old and may need replacing, but I am one who likes to get all the mileage possible out of my computers.

If you are having trouble connecting to and using websites with your older version of Safari, try it with a newer third party browser that is still being updated to meet current internet security protocols.

I suggest you take a look at Firefox browser or Brave browser.

Download an alternative browser and install it into your Applications folder. Launch and use that when you encounter websites that don't play well with Safari.

Your 2012 iMac is at the end of its upgrade path with macOS 10.15.7 Catalina.

There are no further upgrades to be installed.

The macOS version you can upgrade to depends on the year your Mac was released.

✅ Check the compatibility of your Mac hardware with newer versions of macOS software:

➡️ macOS 10.15 Catalina is compatible with the Macs listed here

➡️ macOS 11 Big Sur is compatible with the Macs listed here

➡️ macOS 12 Monterey is compatible with the Macs listed here

You're welcome, my friend.

I hope you can squeeze a little more use from that iMac. 🙂