OS Compatibility for External Drive

Question

OS Compatibility for External Drive

I’m trying to install Monterey on an external harddrive, so I can use it to boot my 2015 MacBook - the latest os it was able to update to was Monterey. But I’m using a new MacBook to set this up & I can’t install Monterey from the new MacBook, because it’s too old. So it seems like I need another adapter cable, so I can use my USB installer to install Monterey directly onto the external harddrive. But before I go out & get one I was wondering, what if I install something more recent that works with the new MacBook? Would I still be able to use it to boot the old MacBook? I’m hoping I can still recover some stuff that wasn’t backed up

MacBook Pro 13″, macOS 10.14

Posted on Nov 3, 2025 2:55 PM

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Answer 1

Top-ranking reply

Servant of Cats

Level 7

33,527 points

Nov 3, 2025 5:10 PM in response to MartinR

MartinR wrote:

Is that your main goal? There should be no need to upgrade or install Monterey on your 2015 MacBook in order to recover (copy) files from it to any Mac.

Which raises the question – can the OP start up the 2015 MacBook from its internal drive? If not, why not?

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Answer 2

MartinR

Level 7

24,053 points

Nov 3, 2025 5:00 PM in response to ninjaphrodite

Pls. identify the specific model of your "2015 Macbook." Some 2015 MacBooks can only be upgraded to Big Sur.

Even so, in order to install Monterey on an external drive to use as a bootable drive with your 2015 MacBook (assuming it's qualified for Monterey) you will need to 1) make sure you have the original Apple drive (SSD) in the 2015 Macbook and 2) install Monterey on the external drive while it is connected to your 2015 MacBook. You cannot accomplish this by installing Monterey on the external drive from the "new" MacBook.

ninjaprhodite wrote

I’m hoping I can still recover some stuff that wasn’t backed up

Is that your main goal? There should be no need to upgrade or install Monterey on your 2015 MacBook in order to recover (copy) files from it to any Mac.

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