How to Start Windows 10 in Safe Mode?

To start Windows 10 in Safe Mode, follow these steps:

1. Hold the Shift key while clicking Restart from the Shut down or sign out menu (accessible from the Start menu or the sign-in screen).
2. After your PC restarts to the "Choose an option" screen, select Troubleshoot.
3. In the Troubleshoot menu, select Advanced options.
4. In the Advanced options menu, select Startup Settings. If you don't see Startup Settings, select "See more recovery options".
5. Click Restart.
6. After your PC restarts, a list of options will appear. Press 4 or F4 or Fn+F4 (you may need to press the Function key along with F4, depending on your keyboard) to start your PC in Safe Mode. Pressing 5 or F5 or Fn+F5 will start Safe Mode with Networking. Pressing 6 or F6 or Fn+F6 will start Safe Mode with Command Prompt.

Essentially, you're triggering an advanced startup option through a specific restart process, followed by selecting the Safe Mode option from the presented menu. This allows you to boot Windows 10 with a minimal set of drivers and services, useful for troubleshooting issues.