Simplest and safest way to do a clean install of a newer MacOS? I currently have El Capitan, but no DVDs
In a nutshell, it seems you need an overview of how to do this. All macos versions from the App Store have a built in utility section where you can open terminal and run createosinstaller script to make a bootable USB installer from the downloaded installer app. Most do not require an AppleID in the App Store, but you might have to set that up as well. You’ll want one, so be sure you write down your security questions and be prepared to enter payment info if requested. It won’t be charged, but you will have to enter it if your machine doesn’t let you make a payment-free account as part of your first free app download.

You do need a USB drive that will be wiped totally - 8 GB is probably large enough, 16 for sure is enough. It doesn’t need to be fast, just needs to work well enough to store 5+ GB of new data and be erased one time.

Here goes:


I recommend the newest OS you can - so open the App Store and try to download Catalina.
If that fails, you’ll need to check the requirements for your mac: https://support.apple.com/en-us/HT210222 _(hint both models of 2012 Air are eligible for Catalina, so you don’t need to use the next step unless you need an older OS)
Then get the installer that’s older than Catalina but meets your requirements - How can I download an older version of OS X/macOS?


Once the installer is downloaded, follow Apple instructions to make the bootable USB: https://support.apple.com/en-us/HT201372

When you boot from recovery (try booting from internet recovery just in case your 2012 model can internet boot - you can skip everything above)

Either way, choose the erase install path in this document whether you internet boot or recovery boot or make USB installer:


https://support.apple.com/en-us/HT204904