Unable to reinstall OS X El Capitan
I’m trading in my MacBook and I’m trying to reset it and reinstall but it’s not happening
MacBook Air
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The age of your MacBook affects what you can install.
September 20, 2016 and later machines can't run El Capitan.
September 30, 2015 to September 19, 2016 internet restore with command-option-shift-R can install El Capitan after wiping the hard drive with Disk Utility HFS Extended. APFS does not support El Capitan
July 20th 2011 to September 29, 2015 can do the same thing, but you need to follow these steps to upgrade back to El Capitan:
https://discussions.apple.com/docs/DOC-8811
Older Macs gets a little more complicated, as this tip explains: