Troubleshooting Graphics and Display Issues on Your Mac

What to Do When Your Display Goes Wonky

Macbook with colorful display
Graphic issues can be as simple as strange colors, or shearing of objects. StockFinland/iStock

I have to say that seeing a Mac's display suddenly appear distorted, frozen, or simply not turning on is one of the worst problems to come across when all you want to do is work on your Mac. Unlike most other Mac issues, this is one you can't put off to deal with later.

Having your Mac's display suddenly start misbehaving can be scary, but before you start wondering how much it will cost to fix, take a moment and remember: many times a display glitch is just that; a glitch, temporary in nature, and not necessarily an indication of continuing troubles to come.

As an example, I've seen my iMac display suddenly show a couple of rows of distorted color; not quite a band of distortion, since it didn't show edge-to-edge. A few other times I've had a window that I was dragging suddenly leave a seemingly permanent trail of smeared images behind as it was dragged about. In both cases, the graphics issues were temporary and did not return after a restart.

One of the more frightening display problems I've run into was when the display never turned on, remaining black, never showing a sign of life. Happily, this turned out not to be a display issue but instead a peripheral that was causing the startup process to freeze before the display was initialized by the system.

My point is, don’t think the worst until you've run through these troubleshooting tips.

Before you start the troubleshooting process, you should take a moment to ensure the graphics problem you're having is indeed a graphics issue and not one of the many startup issues that manifest themselves as a display that's stuck in a gray screen or a blue or black screen.

Make Sure Your Mac's Display Is Plugged In and Turned On

This may seem obvious, but if you're using a separate display, one not built into your Mac, you should check that it's turned on, the brightness is turned up, and that it's properly connected to your Mac. You may scoff at the idea that a cable came loose or the power somehow got turned off. But kids, adults, and pets have all been known to accidentally unplug a cable or two, push a power button, or walk across a power strip switch.

If you're using a display that is an integral part of your Mac, make sure the brightness is set correctly. Our cat has turned down the brightness numerous times, and now that's the first thing I check. (The brightness setting, not the cat.)

Restart Your Mac

Have you tried turning it off and back on again? You'd be amazed how many times this actually fixes issues such as display problems. Restarting your Mac puts everything back to a known state; it clears out both the system and graphics RAM, resets the GPU (Graphics Processing Unit) as well as the CPU, and then starts everything back up in orderly steps.

Reset the PRAM/NVRAM

The PRAM (Parameter RAM) or NVRAM (Non-Volatile RAM) contains the display settings your monitor uses, including resolution, color depth, refresh rate, number of displays, color profile to use, and quite a bit more. If the PRAM or NVRAM (PRAM in older Macs, NVRAM in newer ones) should become corrupt it can change the display settings, causing quite a few issues, including strange colors, not turning on, and more.

You can use the guide: How to Reset Your Mac's PRAM (Parameter RAM) or  NVRAM to reset the PRAM or NVRAM.

Reset the SMC

The SMC (System Management Controller) also plays a role in managing your Mac's display. The SMC controls a built-in display's backlighting, detects ambient lighting and adjusts brightness, controls sleep modes, detects the lid position of MacBooks, and a few other conditions that can affect a Mac's display.

You can perform a reset using the guide: Resetting the SMC (System Management Controller) on Your Mac

Safe Mode

You can use Safe Mode to help isolate graphics issues you may be having. In Safe Mode, your Mac boots into a stripped-down version of the Mac OS that only loads the bare minimum of kernel extensions, disables most fonts, clears out many of the system caches, keeps all startup items for starting, and deletes the dynamic loader cache, which is a known culprit in some display problems.

Before testing in Safe Mode you should disconnect all external peripherals connected to your Mac, except for the keyboard, mouse or trackpad, and, of course, the display.

Use the following tutorial to start your Mac up in Safe Mode: How to Use Your Mac's Safe Boot Option.

Once your Mac restarts in Safe Mode, check to see if any of the graphics anomalies are still occurring. If you're still experiencing the problems, it's beginning to look like a possible hardware issue; jump ahead to the Hardware Issues section, below.

Software Issues

If the graphics problems appear to be gone, then your problem is likely software-related. You should check any new software you've added, including Mac OS software updates, to see if they have any known issues with your Mac model or with software you're using. Most software manufacturers have support sites that you can check. Apple has both a support site and support forums where you can see if other Mac users are reporting similar issues.

If you don’t find any help through the various software support services, you can try diagnosing the issue yourself. Restart your Mac in normal mode, and then run your Mac with just basic apps, such as email and a web browser. If all works well, add any special apps you use that may have helped cause the graphics issue. Continue until you're able to repeat the problem; this may help narrow down the software cause.

On the other hand, if you still have graphics issues even without opening any apps, and the graphics issues were gone when running in Safe Mode, try removing startup items from your user account, or create a new user account to test with.

Hardware Issues

At this point, it's looking like the problem is hardware-related. You should run the Apple Diagnostics to test your Mac's hardware for any issues. You can find instructions at: Using Apple Diagnostics to Troubleshoot Your Mac's Hardware.

Apple has occasionally extended repair programs for specific Mac models; this usually happens when a manufacturing defect is discovered. You should check to see if your Mac is covered under any of these programs. Apple lists any active exchange or repair programs at the bottom of the Mac Support page.

Apple offers hands-on hardware support through its Apple Stores. You can make an appointment at the Genius Bar to have an Apple tech diagnose your Mac's problem, and if you wish, repair your Mac. There is no charge for the diagnostic service, though you do need to bring your Mac to the Apple Store.