Macbook Pro extremely slow when using video chat My Macbook Pro, running on High Sierra, gets extremely slow whenever I'm using video chat. It happens both when using Skype and Zoom. Under normal conditions it's fast and smooth, but as soon as I use video chat things go south and the computer becomes unresponsive and sluggish. 

I think what may be related to it is that I'm using both an external monitor and an iMac (via thunderbolt). But it's strange to me that it all functions correctly when I'm not on video chat, even when I have the laptop screen open as well.

Any ideas what could cause this?

The specs of my computer are:


Macbook Pro (retina, mid 2012) running on OSX 10.13.5
2.3 GHz i7
16GB RAM
256GB SSD
GeForce GT 650M
It is more than likely that the increased demand on the GPU (processing and RAM) by supporting both the external monitor and the MacBook Pro screen while using Skype or Zoom causes the MacBook Pro to lag. Since you mention that the GPU is rather old and has only 1 GB of RAM, this is probably the problem.

Skype may give you the ability to lower the video quality and resolution, putting less demand on the GPU. If you can still Skype with the external monitor disconnected, this may be the best solution.