What is the highest version of OS a late 2014 iMac can upgrade to and how?

Hello, mattkyle99.

Your iMac can run the current version of macOS 11 Big Sur.

How to Upgrade to  macOS 11 Big Sur:

These Mac models are compatible with macOS Big Sur:

• MacBook introduced in 2015 or later

• MacBook Air introduced in 2013 or later

• MacBook Pro introduced in late 2013 or later

• Mac mini introduced in 2014 or later

• iMac introduced in 2014 or later

• iMac Pro

• Mac Pro introduced in 2013 or later

To find the details about your Mac model, click the Apple  icon at the top left of your screen and choose About This Mac.

❗️– IMPORTANT – Backup your data. (You’ve been warned.)

Learn How to Back up your Mac with Time Machine:

https://support.apple.com/en-us/HT201250

❗️ – IMPORTANT – Your 32-bit apps won’t work in Big Sur!

Get this free utility to check the compatibility of your apps:

St. Claire Software – Go64: https://www.stclairsoft.com/Go64/

📚 – Check Compatibility of your Mac with macOS Big Sur.

https://support.apple.com/en-us/HT211238

✅ - Download the macOS 10.11 Big Sur upgrade installer here:

https://apps.apple.com/us/app/macos-big-sur/id1526878132?mt=12

(Don’t use FireFox for this link)

The download will place the "Install macOS Big Sur" application in the Applications folder. Double-click the installer to begin the upgrade process.

D.I. Johnson — macOS Big Sur is version 11, not 10.11. 10.11 is OS X El Capitan.

-Jack

Yep. Thx. Typo. 👍🏽

Tips How to Upgrade to Big Sur Worth checking before attempting the upgrade