Note: Windows Users: If you need assistance on booting your Windows computer into Safe Mode, you can find out more on how to do so in the following article. Taken together, these changes can help resolve software or directory issues that may exist on the startup volume. A cache with issues may cause a blue screen on startup, particularly after a Software Update.

Mac OS X v10.5.6 or later: A Safe Boot deletes the dynamic loader shared cache at (/var/db/dyld/).

Disables all startup items and login items (Mac OS X v10.4 or later).Moves to the Trash all font caches normally stored in /Library/Caches//(uid)/, where (uid) is a user ID number such as 501 (Mac OS X v10.4 or later).From reseting your NVRAM, starting up in safe mode, booting your Mac from a CD or DVD, switching bootable volumes and drives on system start, to forcing media to eject from a superdrive, this list has you covered. Disables all fonts other than those in /System/Library/Fonts (Mac OS X v10.4 or later) This is a list of eleven startup key commands that every Intel Mac owner should make note of.In Mac OS X v10.3.9 or earlier, Safe Mode runs only Apple-installed startup items (such items may be installed either in /Library/StartupItems or in /System/Library/StartupItems these are different than user-selected account login items).Loads only required kernel extensions (some of the items in /System/Library/Extensions).

You may see a progress bar on the screen during this check, and the computer may take longer than usual to complete its startup process Forces a directory check of the startup volume.Starting up into Safe Mode on your Mac computer does several things:

10 mac startup commands