Your external monitor flickers or keeps blanking out

Why it happens

Most monitor flicker comes from the connection, not the Mac. A cable, adapter or hub that can't carry enough signal for the resolution and refresh rate makes the picture drop out for a moment. A refresh rate the monitor handles badly, or HDR on a monitor that struggles with it, can cause it too.

How to fix it

1. Unplug the cable at both ends and push it back in firmly. If you use a hub, dock or adapter, try plugging the monitor straight into the Mac.

2. Swap in another cable, ideally a short certified one. Use a Thunderbolt, DisplayPort or HDMI 2.1 cable for high resolutions or high refresh rates, and try a different port on the Mac.

3. Open the Apple menu, choose System Settings and click Displays. Select the external monitor and choose another option from Refresh rate. A rate that's too low can flicker, so check the monitor's manual for the rate it's made for.

   Displays›Refresh rate

4. If you see High Dynamic Range for that monitor, turn it off and watch for a minute.

   Displays›High Dynamic Range

Still not fixed?

1. Pick a different resolution for the monitor in Displays. Some monitors flicker at scaled sizes but are steady at their native one.

   Displays›Resolution

2. Check the monitor's own menu. Turn off power saving, eco or overdrive modes, and look on the maker's website for a firmware update.

3. Install any waiting macOS update in General > Software Update, then restart with the monitor connected.

   General›Software Update

4. Test the monitor with another computer. If it flickers there too, the monitor needs a repair from its maker.

5. If it's steady elsewhere but flickers on your Mac with every cable and port, or your Mac's own screen flickers as well, contact Apple Support. The Mac may need a hardware check.