Your Mac has special startup modes that help you isolate and fix some issues. You can start up from macOS Recovery and use its repair and recovery utilities, or use safe mode to help resolve issues that might keep your Mac from completely starting up. You can also let occasional users log in to your Mac as guests.
In each of these modes, the graphics performance of your Mac is limited. This is expected behavior. You might see these differences in graphics performance until you restart your Mac or log in to a regular user account:
- Vertical screen "tearing" during window transitions or window dragging
- Sections of the screen, such as scroll bars or the Safari progress bar, that flash or appear to flicker
- Overall slower video performance
- General graphics distortion or video anomalies