Safe mode

In safe mode, an operating system has reduced functionality, but the task of isolating problems is easier since many non-core components are disabled, such as sound.

Though it varies by operating system, safe mode typically loads only essential executable modules and disables devices except for those necessary to display information and accept input.

For example, on Microsoft Windows, the user can also choose to boot to the Recovery Console, a small text-based troubleshooting mode kept separate from the main operating system (which can also be accessed by booting the install CD) or to various "safe mode" options that run the dysfunctional OS but with features, such as video drivers, audio, and networking, disabled.

Safe mode typically provides access to utility and diagnostic programs so a user can troubleshoot what is preventing the operating system from working normally.

[5] In macOS holding the shift key after powering up activates Safe Boot that has background maintenance features (Besides the mode selection, it runs a file system repair, and in Mac OS 10.4, it disables all fonts other than those in /System/Library/Fonts, moves to the Trash all font caches normally stored in /Library/Caches/com.apple.ATS/(uid)/, where (uid) is a user ID number such as 501, and disables all startup items and any Login Items).

On the Classic Mac OS versions 6, 7, 8, and 9, a similar mode to the Unix root is achieved by holding down the shift key while booting, which starts the system without extensions.