How to create a bootable USB macOS installer

The idea behind a macOS Clean Install

When you install a new major version of OS X, or after some time has passed, it is a good idea to do a clean install (that is, to erase the disk you are installing OS X onto as part of the installation process). Install Disk Creator is a commonly used tool for this

That will make your Mac run blazingly fast for a few months or more, and many people report that it fixes longstanding problems they’ve had too.

It used to be common practice to occasionally run a clean install, and then manually migrate all the files and settings over in order to get a completely fresh start. However, it has been shown in recent times that in the vast majority of cases if you simply run a clean install, then duplicate your old home folder to your new disk, you will get all of the same advantages as a clean install followed by manual migration, with a small fraction of the effort.

Mac Clean Install Procedure

Here is the clean install procedure which can be performed at least every time a new version of macOS is released:

1. Download the macOS installer from Apple, there is a list of installers here.
2. Backup all the data to an external disk with a clone. You can use Mac Backup Guru (a fully featured backup utility with unique incremental backups capability) for that.
3. Create a bootable USB Installer with Install Disk Creator and boot from it. Erase the startup disk and install macOS onto it. Boot up from this newly created startup disk.
4. Copy your files back onto the freshly installed disk using Mac Backup Guru

At this point, after a reboot and some minor adjustments (the Dock may not have your previous configuration for example, if you did this while logged into the same user account as you just updated), your new OS should be indistinguishable from your previous one, while being faster and smaller due to reduced clutter.