How to Download macOS Updates to an External Hard Drive

external hard drivemac

My work MacBook Air (2017 MacBook Air with 120gb hard drive) has a pathetically small internal hard drive, to the point where I have to uninstall Xcode and everything else before I can update macOS.

I would be embarrassed to sell a mainstream laptop with a hard drive this small. Shameful.

I have a larger external hard drive, and I'd like to put the update on it so I can run it from there, instead of the internal hard drive.

I don't see any option to download the update outside of macOS, and no option to change where the update is saved to.

Best Answer

Apple appears to have discontinued the practice of making "delta" and "combo" updaters available on their support website starting with macOS 11 Big Sur, and so all updates after the OS X era are only available to download from the AppStore, Software Update System preference, and the command line utility.

If you have a second Mac with sufficient space to download and a USB drive that you are willing to erase, you might be able to create a bootable USB drive (or partition of one). Grab the installer either from the AppStore or the softwareupdate --fetch-full-installer 12.3 (use --list-full-installers to find a different version), and follow the steps in this Apple Knowledge Base article: https://support.apple.com/en-us/HT201372

Possibly booting to Internet Recovery Mode might get you a full installer, but I'm not sure how it behaves with a nearly full disk. https://support.apple.com/en-us/HT204904 "On an Intel-based Mac, … you can use Option-Command-R during startup to be offered either the latest macOS that is compatible with your Mac"

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