Safe mode

Safe mode (initially known as Fail-safe mode or Clean start) is a recovery feature of Microsoft Windows which allows to start the operating system in a light-weight configuration. It enables only the most essential services and drivers, whose list is stored in the registry, and forces the default basic video driver, which makes it useful for troubleshooting driver and configuration issues. The main difference between Windows Recovery Environment and safe mode is that while the recovery environment is a Windows PE distribution stored on a separate partition and is accessible as long as the boot manager is functional, safe mode operates on the main Windows installation and requires the core system components to be intact and functional.

It was introduced in Windows 95, but was not included in NT-based versions. Instead, NT included an option to use the "last known good configuration" to boot the system, up until at least Windows 2000 build 1738.1.

It evolved from a similar feature in MS-DOS 6, which allowed the user to press the F8 key during boot to enter an interactive startup mode, where the operating system would print out each statement in  and   and ask whether should it be executed, or the F5 key to skip parsing of the configuration files completely.

In Windows 10, safe mode includes the following configurations:
 * Safe Mode, which loads only services and drivers whitelisted in.
 * Safe Mode with Networking, which loads only services and drivers whitelisted in.
 * Safe Mode with Command Prompt, which is the same as regular Safe Mode, but runs the executable specified in the  string value in   (set to   by default, hence the name) instead of the regular shell.
 * Directory Services Restore Mode (DSRM), which takes the Active Directory server offline for restoring AD backups. However, this only affects domain controllers, as on normal devices, it has the same function as Safe Mode with Networking. Additionally, it activates the /SOS argument in  (until Windows XP/Server 2003 R2) or in the BCD (at least Windows Vista/Server 2008), which shows the build number, the amount of system processors and the message that the device is booting into Safe mode, in a similar manner to Windows NT 4.0 and earlier. Also known as Active Directory Repair.

Upon booting a system in safe mode and logging in, the system displays a notice about its purpose. Safe mode also sets the desktop background to a solid black color and displays a distinctive watermark that includes the words "Safe Mode" in each corner and the operating system version at the top center. This overrides other forms of watermark, if any. In Windows 9x, safe mode doesn't change the desktop background nor display the system version on the desktop (unless the user uses a pre-release/debug version, or it's manually enabled via registry; the version will appear in the bottom right corner unlike in NT versions), though it still shows the label "Safe mode" in each corner of the desktop and displays a notice after boot up.

Additionally, the system bumps down the screen resolution on Windows XP and earlier to the usual VGA size (640x480), due to it loading the standard display drivers, whereas from Vista to 8.1 it uses a more advanced resolution of 800x600 and in Windows 10 and later uses a resolution of 1024x768 that however can be set back down to 800x600.

Lastly, visual styles are disabled until Windows 7, forcing to use the Windows Classic theme. However, thanks to the sidebar, pre-reset builds of Windows Longhorn have a themed taskbar. Since Windows 8, where the Windows Classic can no longer be set, the default set theme is utilized, but effects such as animations and window shadows are disabled. In Windows 11, due to the enforcement of the standard display drivers, rounded corners are also not utilized.