When you turn on your Mac the most usual thing is that a progress bar appears with the loading of the system and in a few seconds macOS is working.
But if during the boot process there is a problem or you have started with a certain mode, the Mac will show you a different screen and in the following lines you can learn what each one means.
Different screens that may appear during the boot of a Mac
It is important to mention that the boot process finished when the Finder menu bar appears, the desktop and the MacOS Dock. Until this happens you can not say that it has booted completely and here you can see other screens that may appear during the start of the Mac.
Sometimes black, gray or blue screens may appear during the boot process. This is something completely normal and if everything goes well in a few seconds should show you the login screen.
If after a few seconds you press the start button the computer does not show any screening check that the monitor is on and has brightness. If you have checked this and still nothing appears it is very possible that there is a hardware problem.
If your Mac is password protected (something highly recommended) this screen will be responsible for requesting it before giving you access to the computer.
The login screen will show you your profile picture, wallpaper and the box where you will have to type the password or it will tell you that you can unlock with Touch ID if your Mac has this system.
In addition, in the case of computers with FileVault enabled, it will be in this step when the storage disc will be unlocked in order to access the contents it saves.
A black screen with a forbidden symbol in gray means that the selected boot disk contains macOS, but the Mac cannot execute it for any reason. It may be because it is a version that is not compatible with the hardware or due to a system failure.
In this case, it will be necessary to reinstall the operating system in order to continue with the boot.
As in the previous section, a black screen with a gray question mark will indicate that the selected boot disk is not available or does not contain a Mac operating system.
In this case, it is possible that the hard disk or SSD memory of the computer is damaged or that you have selected a disk that is not present (for example if you use an external disk to boot the Mac).
To solve this problem you will have to check that the selected boot disk is available and that it works well. Otherwise, you will have to replace it and reinstall the operating system.
Planet that rotates
If the Mac does not find a boot disk connected to the computer (either internal or external), it will try to boot with a network boot disk and display a planet Earth spinning to represent that it is trying to connect to a network.
This screen appears when starting the Mac in recovery mode over the Internet, a very useful function to reinstall macOS and also to solve disk or boot problems.
On the Macs where a firmware password is set, the black screen with the padlock icon will appear blank when you try to boot from another disk or volume. Either from an external drive, network drive or recovery disk.
In order to exit this screen, you will have to enter the correct firmware password and the boot process will continue normally.
System lock PIN
If you have blocked the Mac through the Find my Mac function of iCloud, when you boot it you will find a screen with a gray background and a space to type the PIN that you have established in the service of the cloud of Apple.
In order to continue, you will have to type the 6 or 4 digit code so that the boot process can continue normally until the login screen.
We hope that this information will help you to know what happens to your Mac if a boot screen appears that is not what you expected and that you can recover the computer. If you need help, remember that you have comments at your disposal.