What is best way to upgrade/update from High Sierra and to which OS ?

GoodChoices wrote:

My MacBook Pro is 2018 with 2 TB hard drive.

Is it best to go all the way to Sonoma if I have older apps that may not function?

Or is it a possibility to upgrade to not the not so latest OS?

Can I just upgrade to Mojave?

Are the later OSs much better?

If you're trying to preserve access to 32-bit apps, then your choices are pretty much

• High Sierra,
• Mojave, or
• running High Sierra or Mojave within a virtual machine (e.g., using Parallels Desktop, or the free personal use version of VMware Fusion)

All of those require Intel-based Macs.

In terms of compatibility with current applications, you usually want to be running one of the most recent three. The "most recent three" just changed from (Big Sur, Monterey, Ventura) to (Monterey, Ventura, Sonoma). If you were concerned about the possibility that some applications did not properly support Sonoma yet, hanging back on Monterey or Ventura might be a more cautious approach.

If you upgrade to Catalina or later, you'll find that iTunes is gone, replaced by separate apps:

What happened to iTunes? - Apple Support

Be aware that if you upgrade to Catalina 10.15 or later you will also need to update any non-Apple 32-bit apps. See: https://www.stclairsoft.com/Go64/

or

 https://www.macworld.com/article/232735/how-to-check-if-mac-software-is-32-or-64-bit.html

The upgrade to Catalina is the one that is most significant in terms of older apps.

That won't be an issue if you upgrade to Mojave, but you also won't have all of the available security improvements that are available with more recent versions including Sonoma and won't be able to run a current internet browser which has better security.

What you can upgrade to depends on the model year of your MacBook Pro.

The model year of a MacBook Pro is available at Apple menu > About This Mac.

A mid 2010 through late 2011 MacBook Pro can be upgraded to High Sierra 10.13.6 but no later version. See: How to download and install macOS - Apple Support

A mid 2012 through early 2013 MacBook Pro can be upgraded to Catalina 10.15.7 but no later. See: How to download and install macOS - Apple Support

A late 2013 and mid 2014 MacBook Pro can be upgraded to the latest version of Big Sur macOS 11 but no later. See: How to download and install macOS - Apple Support

An early 2015 through 2016 MacBook Pro can be upgraded to the latest version of Monterey macOS 12 but no later. See: How to download and install macOS - Apple Support

A 2017 MacBook Pro can be upgraded to the current version of Ventura macOS 13. See: How to download and install macOS - Apple Support

A 2018 or later MacBook Pro can be upgraded to the current version of Sonoma macOS 14. See: How to upgrade to macOS Sonoma - Apple Support

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

Click the  (Apple) menu at the top of your screen and choose About This Mac.

Check the Compatibility of your Mac with newer versions of macOS:

➡️ macOS 10.14 Mojave is compatible with the Macs listed here

➡️ 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

➡️ macOS 13 Ventura is compatible with the Macs listed here

➡️ macOS 14 Sonoma is compatible with the Macs listed here

❗️ – IMPORTANT – None of your 32-bit apps will work in macOS Catalina or newer. This includes MS Office apps and any other older software apps and drivers. These will require that you find 64-bit updates and/or replacement titles.

32-bit app compatibility with macOS High Sierra 10.13.4 and later - Apple Support

Use the free utility Go64 to check the 64-bit compatibility of your apps:

https://www.stclairsoft.com/Go64/

✅ - Download the appropriate macOS upgrade installer app:

Click > 10.14 Mojave,  10.15 Catalina,  macOS 11 Big Sur,  macOS 12 Monterey,  macOS 13 Ventura  or  macOS 14 Sonoma.

Once downloaded, double-click the “Install macOS…” app in the Applications folder to begin the upgrade.

Please see > How to download macOS - Apple Support.