Can my MacBook Air, circa 2012, be upgraded to support a new OS? currently on High Sierra.

The 2012 MacBook Air is limited to macOS Catalina, nothing newer.

The 2013 MacBook Air us capable of running up to macOS Big Sur... not sure about Monterey.

❗️ Do NOT upgrade until you have made a Time Machine or other backup of your startup drive.

Learn How to Back up your Mac with Time Machine

How to Upgrade  macOS:

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

❗️ – IMPORTANT – None of your 32-bit apps will work in Catalina, Big Sur or Monterey.

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

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

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

✅ - IF your Mac and apps are compatible, then using Safari only, download the macOS upgrade installer app:

Click > High Sierra,  Mojave,  Catalina.

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

Please see > How to get old versions of macOS.