How do I create a bootable macOS?

The Easy Option: Disk Creator
  1. Download the macOS Sierra installer and Disk Creator.
  2. Insert an 8GB (or larger) flash drive. …
  3. Open Disc Creator and click the “Select the OS X Installer” button.
  4. Find the Sierra installer file. …
  5. Select your flash drive from the drop-down menu.
  6. Click “Create Installer.”

How do I make a bootable USB for Catalina Mac?

Make a bootable installer drive: The quick way
  1. Connect your drive to your Mac.
  2. Launch Install Disk Creator.
  3. In the main window, you’ll see a pop-up menu under Select the volume to become the installer. …
  4. Under the pop-up menu, you’ll see Select the OS X installer. …
  5. When you’re ready, click Create installer.