I have an issue on my MacBook Pro (15-inch, mid 2010, macOS Sierra).

Some applications won't open, or don't work as expected, and generally I see the spinning pinwheel and macOS is really slow.

Also, often when I shut down I see a black screen, but not completely turned off, so I have to shut down by pressing the power button for 3-4 seconds.

Sometimes applications like Google Chrome or Final Cut Pro don't work well, often freezing up or not opening.

But all these issues disappear if I boot up in safe mode (applications work well, restarting and shutdown always work, no frozen apps, etc).

I tried to:

My question is: What differences are there between safe mode and standard mode? What can I disable to isolate the issue?

  • 1
    Run Hardware Test. Hold D or option-D and turn on the mac. Let go once the test or "starting" symbol appears Jul 7, 2017 at 1:06
  • I tried, but the Apple HW Test doesn't start and returns a " -3403D" error code
    – Giordano
    Jul 14, 2017 at 10:19
  • Sounds like a bad HDD/SSD to me. Try option-D or CMD-D for internet diagnostics. Jul 14, 2017 at 14:39

3 Answers 3


One place to start is testing your Startup/Login items, as it's likely to be something that's getting loaded during normal startup (e.g. a Startup/Login item, a font you've installed, etc) that's causing the problem.

So I would:

  1. Startup normally
  2. Go to System Preferences > Users & Groups
  3. Select the Login Items tab
  4. Take a note of your Login Items
  5. Now remove all of them by highlighting them and clicking on the - button below
  6. Restart your computer

Now your Mac will boot up without those login items loading. Test this and see if the problem persists.

  • If the problem does persist, I'd then remove any fonts you've installed yourself.
  • If the problem goes away you know one (or more) of the Login items were causing the problem. You can then go back and add them back one by one until you've identified the culprit.

Let me know how you go.


I forgot to answer your question about what the difference is between booting into Safe Mode and booting normally. In a nutshell, booting into Safe Mode:

  • doesn't load Login Items and any custom fonts you've installed (which is what my answer above is based on)
  • ensures that only macOS kernel extensions are loaded
  • runs a number of additional checks during startup (e.g. verifying/repairing your drive's directory, etc)
  • deletes various caches

The last two can result in your system effectively repairing itself if your problems are related to corrupted caches or directory issues. In your case, since the problems didn't go away after previously booting into Safe Mode, the problem is most likely related to Login Items or 3rd party kernel extensions.

  • Thanks for answering Monomeeth. I removed every login items (actually there was only Spotify), restarted my computer, but the issue persists.
    – Giordano
    Jul 14, 2017 at 10:28
  • I've restored standard fonts and tested again. The issue is still there.
    – Giordano
    Jul 14, 2017 at 10:36
  • How can I view/check the 3rd party kernel extensions installed on this machine?
    – Giordano
    Jul 14, 2017 at 10:36
  • 2
    You can enter the following command into Terminal: kextstat | grep -v com.apple to list 3rd party kernel extensions. You may want to copy and paste the command so you get it exactly right. In case you don't know, Terminal is found within the Utilities folder, which itself is found within the Applications folder.
    – Monomeeth
    Jul 14, 2017 at 10:37
  • 2
    After several trials, I found that uninstalling completely Flash Player from all the browsers fixed the slowness issue.
    – Giordano
    Nov 23, 2017 at 10:25

this solution might be weird but it worked for me. Turn off your Wi-Fi and try to open your applications again.


My problem was running icloud. Once it was disabled, the computer runs as expected.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .