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:

  1. Fully shut down your iMac
  2. Restart your iMac
  3. Immediately press the Shift key and keep it down
  4. 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).
  5. Take a note of what happens (i.e. do you still notice the lag)
  6. Exit Safe Mode by restarting your iMac as normal
  7. 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.

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  • 1
    Thanks for your suggestion. I did restart in Safe Mode, and the issue went away. (I did notice that my preferred text font, Source Code Pro was not available …?). I then restarted normally, and many of the applications didn’t start automatically, which is no loss. Typing is now OK, so it may be one of the unstarted applications or it may be Safe Mode did the trick, for some reason. After some more testing I will report back. – Manngo Oct 9 '17 at 3:35
  • So far so good. Do you think that just starting in Safe Mode could have solved the problem? – Manngo Oct 9 '17 at 8:05
  • Yes, it is possible. Starting in Safe Mode does a number of things, two of which impact your Mac even after you've booted normally, namely that the system deletes a whole heap of caches and verifies/repairs your drive's directory. – Monomeeth Oct 9 '17 at 8:12
  • Hmm, this didn't make any difference for me. – Steve Bennett Jan 9 '18 at 23:29

I'll put this as an separate answer, @Manngo comment was pointing me to solution.

In my case, in PhpStorm typing was horribly slow/laggy, after changed IDE font from Source Code Pro to other font, slowness disappeared.

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  • Cannot thank you enough - it appears the use of Source Code Pro was causing a very slight lag in places like iTerm and my IDE. Was blaming it on my wireless keyboard, this saved me the $$ of purchasing another one! – josh-cain Jul 13 at 14:53

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