Reinstall mac os without os?

First thing and is important for the following steps to work.

The Age of this computer will Govern what newer version of macOS it will Qualify to install. Use About this Mac from the Apple Icon on Desktop - the required Information will be there

Then choose the version of macOS this computer Qualifies to run.

To perform this action will require booting from a Bootable Installer. 

This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer. Example : Bootable Installer of ??? would have to be done on a computer that Qualifies to run ???

Once that is done read on for preparing the Destination computer  >>

Only works on Intel Based Apple Computers.

1 - Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.

2- Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive. 

3 - It will present options >> Disk Utilities >> View >> View ALL attached Drives. 

4 - Choose the Upper Most Drive ( not the volumes indented and list below ).

5 - The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map. 

6 - Once that is done >> backup out of Disk Utilities and choose install macOS. 

7 - Follow the prompts and it may automatically reboot several time. 

8 - Upon a final reboot - Setup Assist will present with the newer version of macOS.

zarrar195 wrote:

Hi everyone

So i have an old macbook pro, which has no operating system installed and it doesnt have a disk drive either and i dont know how to make a bootable usb. I was wondering if i use the shortcut to install it with the version it came with (10.9 Mavericks) and wanted to ask if it works if there isnt an os installed?

thanks,

Zarrar

If there is no internal drive as you mentioned above - there is no way to install any version of OS X or macOS at all.

Welcome and thank you too.

IMPORTANT CORRECTION to Point 5 above

Mojave macOS 10.14, Catalina macOS 10.15, Big Sur macOS 11 and Monterey macOS 12 - Require formatting as APFS and GUID

High Sierra macOS 10.13, Sierra macOS 10.12 and all those lower - Require formatting as HFS Journaled and GUID.