I have a MacBook Air 2015 can we update it

An early 2015 MacBook Air can be upgraded to the latest version of Monterey macOS 12 or earlier. See: How to download macOS - 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.macworld.com/article/232735/how-to-check-if-mac-software-is-32-or-64-bit.html

Back up your data, check the application compatibility table, click here, and then on the download link for a more-recent OS. That model's maximum one is Monterey.

Catalina and higher won't run 32-bit software; if you upgrade to one of them, use Go64 as well.

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