The storage on my 13 inch Macbook Air 2018 is full. I need to upgrade the OS which is running Big Sur. 58.23 GB is "other" and system is 15.53 Gb. I have bought a portable, external SSD. Can anyone point me to a simple step by step guide as to how to use this?
Hey there HectorPector,
Thanks for reaching out to the Apple Support Communities.
For the best steps on how to install macOS on an external drive, check out this link here: How to reinstall macOS - Apple Support
If you're not using a Mac with Apple silicon, you're using an Intel-based Mac.
1. Press and release the power button to turn on your Mac.
2. Immediately after releasing the power button, press and hold one of these key combinations. If none of them work, review the guidelines for using startup-key combinations.
* Command-R: When you press and hold these two keys at startup, macOS Recovery will offer the current version of the most recently installed macOS.
* Option-Command-R: When you press and hold these three keys at startup, macOS Recovery might offer the latest macOS that is compatible with your Mac.
* Shift-Option-Command-R: When you press and hold these four keys at startup, macOS Recovery might offer the macOS that came with your Mac, or the closest version still available.
3. Keep holding the keys until you see an Apple logo or spinning globe.
4. You might be asked to select a Wi-Fi network or attach a network cable. To select a Wi-Fi network, use the Wi-Fi menuin the upper-right corner of the screen.
5. If you're asked to select a user you know the password for, select the user. Then click Next and enter that user's administrator password, which is the password they use to log in to the Mac.
Reinstall macOS from macOS Recovery
When you see a window with the option to reinstall macOS, your Mac has started up from Recovery.
1. Select the option to reinstall macOS.*
2. Click Continue, then follow the onscreen instructions.
* If the installer asks to unlock your disk, enter the password that you use to log in to your Mac.
* If the installer offers the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.
* If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
3. Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
4. When installation is complete, your Mac might start up to a setup assistant. Follow the steps in the setup assistant.
If you're selling, trading in, or giving away your Mac, quit the setup assistant without completing setup, then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.
As stated in the bullet point of step two under the "Reinstall macOS from macOS Recovery" if you don't see your external SSD when choosing an installation disk, you may need to erase and reformat your SSD in order to see your disk in macOS Recovery. For details on which disk partition scheme would need to be used, as well as steps on how to reformat your SSD, check out these links below:
If you're able to get macOS installed without issues on your external SSD, check out this last resource on how to change your Mac startup disk so you boot from the SSD directly: Change your Mac startup disk - Apple Support
Let us know if that's able to help.
Take care!
Hey there HectorPector,
Thanks for reaching out to the Apple Support Communities.
For the best steps on how to install macOS on an external drive, check out this link here: How to reinstall macOS - Apple Support
If you're not using a Mac with Apple silicon, you're using an Intel-based Mac.
1. Press and release the power button to turn on your Mac.
2. Immediately after releasing the power button, press and hold one of these key combinations. If none of them work, review the guidelines for using startup-key combinations.
* Command-R: When you press and hold these two keys at startup, macOS Recovery will offer the current version of the most recently installed macOS.
* Option-Command-R: When you press and hold these three keys at startup, macOS Recovery might offer the latest macOS that is compatible with your Mac.
* Shift-Option-Command-R: When you press and hold these four keys at startup, macOS Recovery might offer the macOS that came with your Mac, or the closest version still available.
3. Keep holding the keys until you see an Apple logo or spinning globe.
4. You might be asked to select a Wi-Fi network or attach a network cable. To select a Wi-Fi network, use the Wi-Fi menu
5. If you're asked to select a user you know the password for, select the user. Then click Next and enter that user's administrator password, which is the password they use to log in to the Mac.
Reinstall macOS from macOS Recovery
When you see a window with the option to reinstall macOS, your Mac has started up from Recovery.
1. Select the option to reinstall macOS.*
2. Click Continue, then follow the onscreen instructions.
* If the installer asks to unlock your disk, enter the password that you use to log in to your Mac.
* If the installer offers the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.
* If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
3. Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
4. When installation is complete, your Mac might start up to a setup assistant. Follow the steps in the setup assistant.
If you're selling, trading in, or giving away your Mac, quit the setup assistant without completing setup, then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.
As stated in the bullet point of step two under the "Reinstall macOS from macOS Recovery" if you don't see your external SSD when choosing an installation disk, you may need to erase and reformat your SSD in order to see your disk in macOS Recovery. For details on which disk partition scheme would need to be used, as well as steps on how to reformat your SSD, check out these links below:
If you're able to get macOS installed without issues on your external SSD, check out this last resource on how to change your Mac startup disk so you boot from the SSD directly: Change your Mac startup disk - Apple Support
Let us know if that's able to help.
Take care!
Update OS on Macbook Air 2018 using external SSD. Memory full.
