Upgrading Mac mini from macOS High Sierra to the latest version

Back up your data, check the application compatibility table, click here, and then on the download link for a newer OS. Its maximum one is Monterey.

Catalina and above won't run 32-bit software and split the functions of iTunes up; if you choose one of them, use Go64 as well.

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I recommend that you go to maximum Mojave for as Neil points out your 32-bit apps wouldn’t work after that. If you are happy to purchase the 64-bit apps that’s another matter but some apps might not be available in 64-bit.

You can always upgrade later if there is a need.

I stopped at Mojave and it does everything I want.

I use Firefox browser, for many reasons, and Mozilla is still providing security updates for Firefox, even for Sierra.

It has just announced it will continue to do that until at least February 2026 when it will be reviewed again.

Just in case you didn’t know you can see which apps are 64 bit or not=32 bit: About this mac/System Report/Software/Applications

Here’s the link to get Mojave etc.

How to download and install macOS - Apple Support

Need_help_give_help wrote:

I use Firefox browser, for many reasons, and Mozilla is still providing security updates for Firefox, even for Sierra.

It has just announced it will continue to do that until at least February 2026 when it will be reviewed again.

Firefox 115 ESR has gotten many "stays of execution" with respect to Mozilla stopping "critical security updates". If I'm not mistaken, Mozilla was originally planning on abandoning those updates in October 2023, two years ago. As far as new features and updates to handle Web page rendering, it's been a long time since Firefox 115 ESR got any of those. The current version of Firefox requires Catalina or later.

As for other third-party browsers – including Google Chrome, and Brave (also built on a Chromium engine) – they typically now require Monterey or higher.

That’s a nuisance but sorry I don’t know why you got that message but perhaps it didn’t fully download.

I have just downloaded, it took about 15 minutes.

It should automatically launch the installer but at the first window go to menu: Install macOS Mojave/Quit install macos

You should have ended up with a file named “Install macOS Mojave.app” at 6.05GB.

If it is not already in your Applications folder then put it there. You could also check its size to be confident it has downloaded completely. Open/Start the installer again.

If that doesn’t work then you could delete the file, remove it from trash and do the download again.

If the app does not disappear after a successful install then I suggest you transfer it to an external drive to keep for another time.

Hope it installs successfully the next time you try.