Your external monitor is stuck at 30Hz or 60Hz on your Mac

Why it happens

A high refresh rate at a high resolution needs a lot of data, and every link in the chain has to carry it: the Mac's port, any adapter or dock, the cable and the monitor's input. If one of them can't, your Mac quietly drops to 60Hz or even 30Hz and the higher choices vanish from the menu. A 4K picture at 30Hz is why the mouse can feel laggy and choppy.

How to fix it

1. Plug the monitor straight into your Mac, without a hub or dock in between. Use a certified DisplayPort, Thunderbolt or USB-C video cable, or an HDMI cable labelled Ultra High Speed for HDMI 2.1.

2. Open the Apple menu, choose System Settings and click Displays. If you have more than one screen, click the external monitor at the top first.

3. Open the Refresh rate pop-up and choose the highest number your monitor supports, such as 120 or 144 Hertz. If it offers a Variable option, that matches the picture to what's on screen.

   Displays›Refresh rate

4. Move a window around quickly to check. At a high refresh rate, the pointer and windows move smoothly.

Still not fixed?

1. Higher rates still missing? Look in the monitor's own on-screen menu. Many gaming monitors need a high refresh mode or the latest DisplayPort version switched on there.

2. Check your Mac's ports. Some Macs' HDMI ports top out at 60Hz at 4K, and many USB-C to HDMI adapters do too. Your Mac's tech specs on Apple's website list what each port can drive.

3. Try a lower resolution. Turn on Show all resolutions and pick a smaller one, then check Refresh rate again. Less detail leaves room for more frames.

   Displays›Resolution›Show all resolutions

4. If high refresh rates disappeared after an update, install any newer one in General > Software Update, and update the monitor's firmware if its maker offers it.

   General›Software Update

5. If a known-good cable plugged straight into the Mac still won't give the rate your Mac's specs promise, try the monitor with another computer. If it fails there too, contact the monitor's maker. If only your Mac is stuck, contact Apple Support.