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If your Mac is having problems, macOS has several keyboard shortcuts you can hold down to restore the system, start in safe mode, run diagnostics, and more . e. . Here's how to use them.
Apple's macOS has long had a variety of keyboard shortcuts that you can hold while starting your Mac. When you start your Mac, you can choose a different startup drive, boot into recovery mode, including Boot Camp Windows, or use one of Apple's built-in Mac utilities. Launch key combinations allow you to choose what will launch when your Mac boots up.
For all launch key combinations, specific keys may vary depending on whether you are using an Apple Silicon based Mac or an Intel Mac.
Startup disk selection
Intel processor. or Apple Silicon Mac.
On Intel Macs, if you hold down the Option key before booting your Mac, but after turning it on, you'll get a graphical boot drive selection menu that lets you interrupt startup to choose what volume to run from. This menu is located in your Mac's firmware and allows you to change boot disks in case your regular boot disk stops loading for some reason:
Internal drives are listed first, followed by USB, Thunderbolt, FireWire, and other external drives. . If any network boot drives are available, they are listed last.
On Apple Silicon Mac computers, the process is similar, but instead of holding down the Option key, press and hold the power button until the list of volumes appears . appears.
If you have an Intel Mac with an Apple T2 Security Chip, you may need to set your security options first using the Startup Security Utility before you can use the Bootable Boot Disk feature. This application allows you to set a firmware password and whether or not you can boot external drives.
There is a full support article on how to use the startup security utility. Also see the Apple article, Set a Firmware Password on Your Mac.
The list of boot disks in the boot disk selection firmware menu is the same as the list of disks displayed on the boot disk control panel in the settings.
If you hold down the Shift keyAfter selecting your startup drive but still pressing Continue or up arrow button, your Mac will start in Safe Mode.
Start in Apple Diagnostics
To start Apple Diagnostics on an Apple Silicon Mac that is also in your Mac's firmware, follow the same procedure as selecting the boot disk above, but instead of going to the selected boot disk, press Command D to enter Diagnostics.
On Intel Mac computers, instead of the previous procedure, simply hold down the D key at startup. This page describes the diagnostic procedure and some of the result codes.
Firmware recovery mode
If for some reason your Mac stops booting, there is also a built-in -in-firmware Recovery Utility. To load the recovery utility, on Intel Mac computers, hold down the Command R keys at startup until you see the Apple logo.
On Apple Silicon Macs, follow the same procedure as selecting the boot drive, but instead of selecting the drive to boot, select the Options gear icon. You will proceed to recovery.
After the restore, you have four options:
Most of them are self-explanatory, with the exception of Reinstall macOS.. In this case, a typical workflow is is to select the Disk Utility option, clean your disk to reinstall macOS, and then Quit from Disk Utility, which will return you to the recovery menu. .
Then select Reinstall macOSto perform a clean install on the drive you just erased. However, please note that erasing a drive will destroy all existing data on it, and there is no way to recover the data. Be careful when using this option.
You can run Reinstall macOS directly to a previously used drive containing data or a copy of macOS. The installer is smart enough not to destroy any data previously created by Apple, and also smart enough to keep any third-party software that may have been previously installed on the drive containing the copy of macOS.
But that doesn't guarantee that you can repair the drive, only that you can install a fresh copy of macOS on it to make it bootable.
To use one of the recovery options, select it from the menu and click Continue. Apple has a full article on how to start Recovery and use it.
Several other recovery options are available on Apple Silicon-based Macs:
- Startup Security Utility
- < strong>Terminal
- Shared Drive
- Boot Drive
See this article for full recovery options on Macs based on Apple Silicon.
Internet recovery mode
If you have an internet connection, you can run it online Recovery Mode is similar to Firmware Recovery Mode, except that it downloads the recovery application from Apple's servers over the Internet. This option may take longer to run for obvious reasons. To start in Internet Recovery Mode, hold down Command+Option+R or Command+Option+Shift+R keys at startup.
To launch in safe mode, just hold down the Shift keyat startup. Safe Mode boots macOS but disables most extensions, drivers, and other third-party software during boot. This feature is useful if you have installed certain software that freezes on startup.
This keyboard shortcut is only available on Intel-based Macs.
Safe Mode can be activated on Apple Silicon by pressing and holding the power button until the message “Loading launch options” appears. With the volume selected, press and hold the Shift key, then click Continue in Safe Mode.
This is the oldest Mac startup option, going back to Mac Plus. Better known as “zapping-PRAM”, if you hold down the Command Option P R key at startup, all settings in “General”, “Mouse” and “Keyboard System Preferences” are reset to their default values.
This also resets settings such as key repeat rate, mouse speed, acceleration, and advanced mouse options. Trackpad settings also revert to default. Some sound settings may also be reset.
This option is only available on Mac computers with an Intel processor. Apple has a lot more information on this topic.
Use this option with care. Some Macs can get into a state where a special chip on the motherboard called the System Management Controller (SMC) becomes confused and refuses to allow startup. The indoor fans are also controlled by the SMC.
Some Macs may experience strange fan speed behavior when a SMC reset is required. In such cases, reset the SMC by holding down the Shift-Control-Option key at startup.
Resetting the SMC is usually enough to get the Mac to boot up again, assuming the boot disk hasn't been corrupted. On some Macs, resetting the SMC may require you to first disconnect and then reconnect the power cord before using the startup key combination.
In earlier versions of macOS than Mojave, you can hold down Command S< /strong> at startup, and only the default administrator account will be available. This was mainly a security feature and is no longer available in macOS Mojave or later versions.
Target disk mode
>T at startup, your Mac will boot into a special mode called Target Disk Mode (TDM). This mode allows you to use your Mac as an external drive on another Mac connected via a USB, USB-C, or Thunderbolt cable.
This feature was originally designed for older Macs with FireWire ports, but it still works today. To use it, connect the two Macs using one of the mentioned cables, restart the Mac you want to use as a drive while holding down T, then open System Preferences->Startup Disk. strong>on another Mac and select the Mac running in TDM as the boot drive.
If you reboot your Mac without TDM, it will boot via cable to the Mac's TDM drive. A dedicated disk icon will appear on the TDM Mac display. Apple has an article on how to transfer files between two Macs using Target Disk Mode. TDM is only available on Mac computers with an Intel processor.
For a similar process on Apple Silicon-based Macs, see this article.
Normally, when your Mac boots up and displays the Apple logo, FreeBSD- Darwin Core System starts up a lot of system services, hardware, drivers, extensions, and loads the main OS.
There is a hidden way to see exactly what Darwin is doing at boot time. Hold down Command V during startup. Instead of the Apple logo, you'll see all the Darwin startup system messages scrolling through as you complete each step. Verbose mode is only available on Mac computers with an Intel processor.
Startup from optical drive
On a Mac with an optical drive, for example internal DVD. R/ROM, press and hold the C button to start from an optical disc. The disk must be bootable and must have a working operating system on it in order to be able to boot from it.
Eject Optical Drive
If you can't start your Mac and you don't have a bootable optical drive stuck in your Mac's internal optical drive, you can eject the disc before starting by holding down mouse/trackpad button or Eject or The F12 key on the keyboard when enabled. This option allows you to insert another optical disc and try booting again.
If for any reason you need to force restart your Mac, you can do so by clicking < strong>power button twice: If your Mac is already on, hold down the power button until it turns off.
After turning off, press the power button againto reboot. Hard restarting your Mac can result in longer boot times on the next restart, as macOS will run some disk checks or restore apps in the background to make sure the OS has been reset to a stable boot state.
Force launch for macOS only
If you previously mounted a non-macOS volume, for example as a Windows volume as your boot drive, instead you can force the macOS volume to be selected by holding down the X key at startup. If your Mac finds a macOS boot volume in the list of volumes, it will start from the first macOS boot volume it finds.
Prevent login items from running
You can stop the launch all login items when logging in, but only if you hold down the Shift key after pressing the login arrow button on the Mac login screen. Note that this is different from the safe mode above because you are holding down the keyShift immediately after pressing the login button rather than holding Shift while turning on your Mac.
Run/install from NetBoot server
Early version Mac OS X Server included networking technologies called NetBoot and NetInstall. The server comes with a separate NetBoot installation CD to add boot functionality to a Mac OS X server. The idea was to store common Mac OS X installation and boot images on the server, and users could install and boot from those images over the network.
It was a brilliant idea, albeit a little slow.
Later, Mac OS X Server became a standalone application for macOS that added all server functionality by simply downloading and running a single server application from the Mac App Store. Apple ended server and NetBoot support in 2021. To start the NetBoot server on Macs that still support it, hold down the N key during startup.
On older Macs, to make the server-hosted NetBoot disk image your boot disk, go to System Preferences->Boot Disk and look for any disk icon with a globe to this:
NetBoot has largely been replaced by a more modern generic network boot technology called PXE that works on most platforms. Oddly enough, third-party developers have kept NetBoot alive by recreating its functionality in some versions of PXE.
There is also a modern NetBoot-like project called netboot.xyz which is based on iPXE for network boot. There is also an old University of Utah article written in 2007 on how to install and configure a NetBoot server.
Ancient history extra credit (boot in OpenFirmware)
If you happen to be near an old Mac with a “NewWorld” ROM from the late 1990s, you can surprise your friends by showing them how to boot into Open Firmware. From the first iMacs and Power Macintosh G3s in 1998 to the transition to Intel processors, Macs used Open Firmware and newer modern ROMs called NewWorld ROMs.
NewWorld kept most of the old Mac OS 9 in ROM on the motherboard, but used Open Firmware for the pre-OS boot sequence.
To boot a Mac from NewWorld ROM into Open Firmware at startup, hold down Command+Option+O+F. You will remain at the Open Firmware command line, but you must know the Open Firmware commands to continue.
After switching to Intel processors, new Macs switched from open firmware to EFI (Extensible Firmware Interface).