MacOS: Annoying lag when typing I have discovered an annoying lag when typing on my Mac. It’s a fraction of a second, but it’s enough that it can be as much as a word behind.

The lag occurs when I use Firefox, Notes or Atom, so it is clearly not related to a single application.

I have recently upgraded to 10.13 High Sierra, as well as the supplementary update. I am running on a current model iMac.

As far as I am aware, I’m not running anything in the background which affects the keyboard. I even have background spelling turned off. And, of course, I have restarted.

This is not apparent on my MacBook which is similarly configured.
The first thing I would try is starting your iMac in Safe Mode as follows:


Fully shut down your iMac
Restart your iMac
Immediately press the Shift key and keep it down 
Let go of the Shift key when you see the login window (NOTE: If you have FileVault enabled you may need to log in twice).
Take a note of what happens (i.e. do you still notice the lag)
Exit Safe Mode by restarting your iMac as normal
Test again to see if the lag still persists


Once you've tried the above let me know if the lag was still noticeable in Safe Mode and also when booted in normally again.