Why your Mac dims video during flashing lights, and how to control it

Why it happens

Dim flashing lights watches video for repeated flashes or strobe effects and darkens the picture while they play. It's there for people who are sensitive to flashing, including people with photosensitive epilepsy. It needs a Mac with Apple silicon, so Intel Macs don't have it.

How to fix it

1. Open the Apple menu, choose System Settings, and click Accessibility in the sidebar.

2. Click Motion and find Dim flashing lights. Turn it on to soften flashing scenes, or off if you'd rather see video at full brightness.

   Accessibility›Motion›Dim flashing lights

3. If anyone who uses this Mac is sensitive to flashing, leave it on. It changes nothing in video without flashes.

Still not fixed?

1. If the screen still gets darker with the switch off, your Mac may be adjusting brightness to the light in the room. Turn off Automatically adjust brightness in Displays to check. It only shows on Macs and displays with a light sensor.

   Displays›Automatically adjust brightness

2. Dim flashing lights may not catch every flash in every app or video. Think of it as an extra layer of care, not a guarantee, and keep any precautions your doctor has suggested.

3. If other movement on screen bothers you, such as windows zooming open, turn on Reduce motion in the same Motion section.

   Accessibility›Motion›Reduce motion

4. If the screen flickers or dims when no video is playing, that may be a display fault. Contact Apple Support or an Apple Authorized Service Provider, because it may be hardware.