If creating a bootable USB drive for macOS is too much a hassle for you then see the steps in a guide below to learn how to clean install Mac OS X / macOS Sierra without USB flash drive to cut time required to get a new OS ready for use on your iMac or MacBook. The method below will allow you to clean install OS X or macOS Sierra on your device without any USB flash drive or external storage device needed to run to the installation files on iMac, MacBook Air and MacBook Pro.
How To Clean Install Mac OS X / macOS Sierra Without USB Drive:
When a clean install of Mac OS / macOS Sierra is needed the first thought that pops up in mind is to grab a bootable device such as USB Flash drive or external storage device for loading and running installer files needed for fresh Mac operating system installation. However, there’s another easy and quick way of clean installing Mac OS on your device without having to first create a bootable flash drive and then installing the OS from it. This method requires only a stable and working internet connection for over-the-air (OTA) installation. The method below is an untethered way of install OS on MAC devices that comes in handy for clean installing OS X or macOS Sierra on occasions such as when you don’t have a USB dongle on you to connect MAC with USB or external storage device, or you have misplaced USB drive on which installation files were saved, or the internet connection is fast enough to support the installation of large files quickly.
Here are the steps needed to clean install macOS Sierra / OS X on your device without USB. But before that, create a backup of your device data on iTunes or iCloud as the process below will erase existing data on your iMac or MacBook.
1 – Turn OFF your MAC, or restart, while holding down the Command + R keys together.
2 – When the Apple logo shows up on the screen, release Command + R keys.
3 – Your MAC will now enter the Recovery mode.
4 – In the Recovery mode, when you see an interface similar to the one shown below, click on the Disk Utility option and hit the Erase button to wipe out content on Mac HDD or SDD. Make sure to erase the data from the drive where you wish to clean install new OS X or macOS.
5 – Close the Disk Utility interface when the disk data wipe out is complete to return to the main Utilities screen.
6 – Now connect your MAC to WiFi network: click the WiFi icon in the menu bar for it.
7 – Enter WiFi network’s name and password. You can also use Ehterner cable to for wired internet connection.
8 – Next, click on the Reinstall macOS or Reinstall OS X in the main ‘Utilities’ screen.
9 – Follow on-screen setup instructions as prompted to complete the setup process. Make sure to select the same drive from where you erased the data in step-4 above.
10 – Wait for the installation process to conclude, which could take several minutes or hours (depending the speed of your internet connection) as the recovery options fetches data from Apple’s servers for downloading macOS or OS X.
11 – Once completed, you can restore backup and make changes as you like to start using macOS Sierra or OS X on your MAC.
12 – That’s all.
There are other ways of installing OS on MAC devices. For that see the links below.