Late 2013 iMac 27" desktop

Even if you did perform the Catalina 10.15.8 update in Feb 2026, the Safari browser version remains at 15.6.1 and dates back to 2020 with a recent modification in 2022. A 4 - 6 year old browser is not going to keep up with the ever changing Internet security and web development changes that have occurred. That will definitely impact what your old version of Safari can access.

The Firefox 156.0 browser still supports macOS Catalina and is more current browser technology than your old version of Safari. The Brave Browser now requires macOS Monterey or later and you cannot upgrade that 2013 iMac further.

VikingOSX wrote:

The Firefox 156.0 browser still supports macOS Catalina and is more current browser technology than your old version of Safari.

Just wanted to add my agreement to the advice VikingOSX gave you, in case you think it was just one person's opinion.

Technology moves on. Even though Catalina itself is still viable, the version of Safari available on Catalina isn't. Firefox is one of your only opportunities to keep using the web on your 2013 iMac. The current version of Firefox is still fully supported on macOS Catalina.

And while Firefox privacy & security is excellent, I suggest adding the Privacy Badger and uBlock Origin plugins (both are free) after you install Firefox. Go to Firefox Browser Add-Ons and use the "Find" box to install them.

I will add that it is time to start considering a new Mac. Your 13-year old iMac is obsolete in many ways especially the hard drive. Make sure you have a good external backup of your data in the event the Mac fails to start one day.

beefbiz wrote:

Why can't my late 2013 iMac desktop be upgraded so safari works with all web sites again?

The iMac (27-inch, Late 2013) originally shipped with Mac OS X 10.8.4 (Mountain Lion). It received seven major macOS upgrades, but macOS 10.15.* (Catalina) is the end of the line.

Catalina is seven major versions behind the current version of macOS – macOS 27 (Golden Gate). The version of Safari you get is tied to the version of iOS, iPadOS, or macOS that you run.

Safari Release Notes | Apple Developer Documentation

For instance, Safari 26.* was available for iOS 26, iPadOS 26, macOS 26 (Tahoe), and the two preceding versions of macOS. And now that macOS 27 is out, Safari 27 is only for macOS 15.* (Sequoia), macOS 26.* (Tahoe), and macOS 27.* (Golden Gate).

Another vote in favor of Firefox.

As far as I know, it is the only major browser whose current version still supports Catalina. The developers of other Web browsers have moved on, and the current versions of most of those browsers require Monterey or better.

The current version of the LibreOffice office suite no longer supports Catalina, but The Document Foundation does maintain an archive of old, unsupported versions. The version of Affinity Studio that is "free with registration" runs on Catalina, as does the commercial program GraphicConveter 12 (if I'm not mistaken). Those might be your only / best choices for photo editors, as even the GNU Image Manipulation Program (GIMP) now requires at least Big Sur.

Be sure to update to the latest version of Catalina before next January. A security certificate is set to expire then, and things like iMessages (text messages to and from other Apple users), FaceTime calls, and maybe other stuff is going to break if you're still running an older release of Catalina when that happens.

As far as I know, no version of macOS prior to Catalina has received a patch for the security certificate issue. My guess is that people with older Macs who are stuck on El Capitan or High Sierra are going to find that things just break.