If, for example, I'm using El Capitan on a MBP, I then install High Sierra on it and the firmware gets updated, will I be able to re-install El Capitan if I decide to do so later?

  • Changing only Captain to Capitan was necessary, I didn't think it's more basic, I wouldn't alter otherwise
    – Marky M.
    Feb 11, 2020 at 14:40

1 Answer 1



It's not the firmware that dictates what OS can be installed, but the Model identifier (i.e. MacBookPro 12,1 for a 2015 13" MacBook Pro).

If your Mac was capable of running a macOS version before, it will continue to be able to support it after a firmware update.

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