Q: Mouse cursor lags with external monitor

I too have faced this issue (occasional stuttering of input devices when external monitor connected), ever since the days of Mavericks. I can't claim to have a certain fix for it, or even be sure of what's causing it, but this is my theory.

The problem is due to the electrical interface between the monitor and the HDMI port. I believe this because it doesn't happen with every monitor, and I also suspect there may be grounding issues with my monitor. Perhaps it's a fundamental chipset incompatibility, I have no idea (the console log gives no clues). The only way I have found to mitigate this, although this may be coincidental, is to make the connection more secure for the plug on the Mac side of the cable. In my case the weight of the cable is pulling down on the plug, making it angle slightly upward, and perhaps causing a less secure connection for all of the pins. I have placed a piece of cardboard under the plug, thick enough that the plug can only enter horizontally. Whilst I do occasionally do encounter lag, I can now go many days without any problems, and in my case the connection still could be more secure, as it moves too far laterally for my comfort.

I would suggest improvising a way to make the connection as secure as possible, and, if after a few days the incident rate falls, then my suggestions would be

• As short an HDMI cable as is necessary. The longer the cable, the more chance of issues.
• A better cable. My cable was the cheapest eBay cable I could find, and whilst it appears to work, the connection doesn't feel as secure as I imagine it should be.

I should also add that when it does start lagging, you can reset the interface by opening the Displays panel in System Preferences. If more than one refresh rate is available, toggle that. If not, rotate the screen (then immediately revert it). It may require more than one application.

Hi guys,

I'm having the same issue as most of you. Searching about it I got in this thread.

I have a MacBook Pro (Retina, 15-inch, Mid 2014) with GeForce GT 750M 2048 and a Samsung LU28E590 4K monitor. I tried a lot of solutions described here. If I work with the mac screen opened the issue goes away (I would prefer to work just with the monitor). My issue is with magic mouse one. I tried with a logitech and it happens too. I have a magic trackpad and it works fine.

I was wondering if with magic mouse 2 the problem goes away.

Anyone got a definitely solution?

I moved my usb wireless adaptor to the other side of my 2013 macbook pro  (away from the HDMI port) and the problem was instantly fixed.

this worked for me. Thanks!