External monitor flickering on macOS Tahoe
Updated
Short answer
Since macOS Tahoe 26, many people report external displays, including Apple's Studio Display, flickering or going black for a moment, and reports continued through 26.1 and 26.2. Some of it is macOS; some is a cable, hub or refresh-rate setting. The way to tell is to record when it happens, then change one thing at a time.
Step by step
- Write down when it happens. Time, which display, and what you were doing: waking the Mac, plugging in power, moving the laptop, watching video. A pattern points to a cause.
- Take the hub or dock out. Connect the monitor straight to the Mac. If the flicker stops, the hub, dock or its cable is the cause.
- Swap the cable. Use the cable that came with the monitor, or a certified Thunderbolt cable. Some people with Thunderbolt video problems on 26.1 reported that a different cable fixed it; many others found it made no difference, which itself points at macOS.
- Fix the refresh rate. In System Settings → Displays, choose a fixed refresh rate (for example 60 Hz) instead of a variable one, and turn off Adaptive-Sync or FreeSync in the monitor's own menu. Variable refresh handshakes are a known cause of black screens and blinking on high-refresh monitors.
- Turn HDR off for a day as a test. Some reports also name True Tone and Night Shift as triggers, so try a day with those off too.
- Update macOS (macOS 27 is out) and, if the maker offers it, the monitor's firmware. Note whether the flicker changes after the update.
- If it continues with a direct cable and fixed refresh, it's likely macOS. Report it with Feedback Assistant, with your times and setup; specific times make a report much more useful.
Flicker or drop?
A flicker you can see may be the display briefly disconnecting and reconnecting (windows may jump between screens), or the picture changing without a disconnect. The first leaves a trace macOS can report; the second often doesn't.