Can I upgrade 2011 iMac to Catalina? Why not?

High Sierra is the limit for 2011 iMacs.

macOS Catalina - Technical Specifications

General Requirements

• OS X 10.9 or later
• 4GB of memory
• 12.5GB of available storage (OS X El Capitan 10.11.5 or later)*
• Some features require an Apple ID; terms apply.
• Some features require a compatible internet service provider; fees may apply.

Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen and choose About This Mac. These Mac models are compatible with macOS Catalina:

• MacBook (Early 2015 or newer)
• MacBook Air (Mid 2012 or newer)
• MacBook Pro (Mid 2012 or newer)
• Mac mini (Late 2012 or newer)
• iMac (Late 2012 or newer)
• iMac Pro (2017)
• Mac Pro (Late 2013 or newer)

Nazfamdon wrote:

I’m mainly concerned because Safari won’t function properly, so I loaded Firefox and Google Chrome to surf effectively.

Well, that's just a Safari problem. Nothing wrong with High Sierra, I'm running Safari on High Sierra and it works fine.

See these Apple Support Topics for detailed advice:

If Safari is slow, stops responding, quits unexpectedly, or has other issues - Apple Support

If Safari doesn't load a page or webpage items are missing - Apple Support

Safari for Mac: If Safari can’t open a website

Have you tried this?

Make a New Location, Using network locations in Mac OS X ...

http://support.apple.com/kb/HT2712


System Preferences>Network, top of window>Locations>Edit Locations, little plus icon, give it a name.

System Preferences>Network, click on the little gear at the bottom next to the + & - icons, (unlock lock first if locked), choose Set Service Order.

The interface that connects to the Internet should be dragged to the top of the list.


If using Wifi, instead of joining your Network from the list, click the WiFi icon at the top, and click join other network. Fill in everything as needed.

System Preferences>Network>choose interface>Advanced>Proxies Tab, make sure none are set, like for HTTP & HTTPS.

System Preferences>Network, unlock the lock if need be, highlight the Interface you use to connect to Internet, click on the advanced button, click on the DNS tab, click on the little plus icon, then add these numbers...

8.8.8.8

8.8.4.4

1.1.1.1

9.9.9.9

Apply.

It doesn't matter if you upgrade the video card (if you even can--it may be soldered to the logic board). It doesn't check the actual hardware. Apple sets the limit based on year manufactured and only checks that.

Why do you feel you must upgrade to Catalina? High Sierra will still work fine and get security updates for at least another year.

Because it doesn't have the necessary hardware.

Sounds like you installed something that is interfering with your browsing in Safari.