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Get help with video issues on external displays connected to your Mac

Try these steps if the image on an external display connected to your Mac is blank or doesn't look the way you expect.

Before you begin

You can resolve many display issues by updating the software on your Apple devices, cables, and adapters. If you can see an image on your screen, check for software updates using the Mac App Store:

1. Connect your external display and any Apple video cables or adapters that you use with it.

2. From the Apple menu, choose App Store.

3. Click the Updates button in the App Store window.

4. Install any macOS or firmware updates that are listed.

If you're using a display, hub, extender, or adapter not made by Apple, check with the manufacturer for any updates that might be available.

If you're trying to connect a 4K display or Ultra HD TV with your Mac, make sure your computer meets the requirements for using these external displays.

If your software and firmware are up to date, or if you can't see the image on your screen, try the steps below for your specific issue.

[pic]

Blank or unusable
display
 

[pic]

Fuzzy or blurry
images
 

[pic]

Contrast or color
issues
 

[pic]

Thunderbolt 3
(USB-C)
 

If the display image is blank or unusable

Try these steps if you don't see an image on your display. These steps can also help if the image on your screen repeatedly turns on and off (flickers), if horizontal lines appear (snow), or if the image is distorted (torn or scrambled). 

These steps likely won't help if the issue is only happening in one app. If you see similar issues in only one window or app, check with the app's developer for updates or more help.

Check connections

Check the connections to your Mac and external displays:

• If you're using an Apple notebook, try connecting its power adapter.

• Make sure the external display's power cable is securely connected and that your display is turned on.

• If you're using a Mac Pro (Late 2013) make sure your displays are connected to the right ports.

• If you're using a display hub, switchbox, or "KVM," try connecting your display's video cable directly to your Mac instead.

• Disconnect the video cable where it plugs into your Mac, then plug it back in to reseat the connection.

• If you're using a video adapter, unplug the video adapter from your Mac, then plug it back in to reseat the connection.

• If you're using more than one video adapter to connect your display (the adapters are "chained" together), try connecting the display using only one adapter if possible. Some video adapters can't be connected together. For example, a mini DisplayPort to DVI adapter can't be connected to a DVI to HDMI adapter.

• If your display has more than one video connection, see if using another connection on the display works. If possible, check to see if using a different display or a different adapter works.

• Try using a different cable that you know is in working order. Check with the display's manufacturer to make sure you're using the cable they recommend.

• Restart the Mac with the display connected.

Detect your display

If you're using an external display, sleep and wake your Mac to make it check for connected displays:

1. Press the power button on your computer to put it to sleep, or choose Apple menu > Sleep.

2. Wait a few moments, then press a key on your keyboard or click your mouse or trackpad to wake your Mac.

If you're using more than one display, and you can see the image on one of the displays, you can also use Displays preferences to check for connected displays.

Adjust video settings

If there's no image on your display, try adjusting your display's brightness or contrast. If there's still no image, or the image appears torn or scrambled, try selecting a different video resolution in System Preferences.

Adjust brightness

• If you're using an Apple Display, press the increase brightness key [pic]  on your Apple keyboard. To adjust the brightness of a secondary display, press Control-F2.

• If you're using a display that's not made by Apple, check the documentation that came with your display to see if it includes built-in controls for adjusting its brightness or contrast.

Change your display resolution

1. From the Apple menu, choose System Preferences.

2. Click the Displays icon.

3. Click Default for display. If you see more than one resolution listed, choose a resolution and refresh rate. If the display turns off when you change resolutions, press the escape key to undo the change. 

4. [pic]

If you can't change the resolution of your display because you can't see an image, restart your Mac in safe mode to reset the display resolution to defaults.

If starting in safe mode doesn't resolve the issue, reset your Mac's NVRAM and SMC to reset the video ports on your Mac to their defaults.

Check for third-party display software

If your display works only when your Mac is started in safe mode, and you have display-related software installed, check with the software's developer for updates, or try temporarily uninstalling it.

•

[pic]

If an image appears fuzzy or blurry

If images or text on your display appear pixelated or blurry, check these things.

Check your display resolution

Make sure your display resolution in System Preferences is set to its default. If you're using a resolution that's scaled, the image might be magnified to fit the display. This can cause the image to look blurry in some apps.

1. From the Apple menu, choose System Preferences.

2. Click the Displays icon.

3. Select Default for display.

4. [pic]

If you use a monitor or an HDTV connected with an HDMI cable, you might see a difference in video quality if your display is set to television mode. Check your display for a "monitor mode" setting to get the best video quality.

Retina displays

If an app you're using appears low resolution on your Retina display, check to see if an update to the app is available. Most apps have been updated to use the higher pixel densities of Retina displays.

Lower-resolution images on some web pages might also appear "softer" when viewed on a Retina display. This is because Retina displays have a higher pixel density and not all websites use Retina-ready images.

For example, the images below look different when viewed on a Retina display, but the same on a non-Retina display. This happens because the Retina-ready image has a higher pixel density:

|[pic] |[pic] |

|Standard image |Retina-ready image |

• Learn more about Retina displays

[pic]

If you see contrast or color issues

If your entire display image seems too dark or too bright, you can adjust the brightness and contrast from the Displays pane of System Preferences, or by using your display's built-in controls.

Adjust brightness and contrast

To adjust the brightness of your Apple display, press the brightness key [pic] or F2 key on your keyboard. You can also use the brightness adjustment for each connected display in System Preferences > Displays.

Displays not made by Apple sometimes have brightness and color adjustments built into the display. Check the documentation for your display to see if it includes built-in controls.

When you connect a display, projector, or HDTV using an HDMI cable, you might see a difference in video quality if your display is set to television mode. Check your device for a "monitor mode" setting to achieve the best video quality.

You can also calibrate each display from the Color tab of Displays preferences to get the best color and brightness from your display.

If you see bright or dark pixels

If individual pixels on your display seem too bright or too dark, see these articles for more help: 

• About LCD display pixel anomalies for Apple products released in 2010 and later

• About LCD display pixel anomalies for Apple products released before 2010

[pic]

Connecting displays with Thunderbolt 3 (USB-C)

The Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter connects 2016 MacBook Pro models with Thunderbolt 3 (USB-C) ports to older devices that use Thunderbolt (10Gbps) or Thunderbolt 2 (20Gbps). For example, this is the adapter that you should use to connect your MacBook Pro to an Apple Thunderbolt Display or a third-party Thunderbolt 2 storage device.

This adapter doesn't support connections to Mini DisplayPort displays, including the following Apple adapters and displays: 

• Apple Mini DisplayPort to Dual-Link DVI Adapter

• Apple Mini DisplayPort to DVI Adapter

• Apple Mini DisplayPort to VGA Adapter

• Apple LED Cinema Display

If you're using the Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter to connect to a compatible display and the display doesn't show an image, try unplugging the adapter and plugging it back in.

[pic]

Get more help

If you've tried these steps and your display still isn't working, contact Apple Support to get more help. 

Diagnostic fees may apply for issues not covered under warranty or the AppleCare Protection Plan (APP).

Mismatched system software

If the Mac is started up from an external drive (or if someone copied a version of macOS from another computer to this Mac), it might be using a build of macOS that's earlier than what this Mac came with. Applying available updates can sometimes resolve the issue if a newer version of macOS is available as a software update. If it doesn't, try starting the Mac from the built-in startup disk instead, or try reinstalling macOS using the Mac App Store, or macOS Recovery.

If the pointer or a moving window stutters on an HDMI display connected to a Mac

If the refresh rate is set too low on your external display, moving the pointer or dragging a window might appear to tear or stutter. See If a pointer or window blinks when viewed on an HDMI display connected to your Mac for more information.

Older displays

If you have an older display, it might need to warm up after it turns on. Older LCD (Liquid Crystal Displays) use CCFL (Cold Cathode Fluorescent) backlights. This kind of lighting can require several minutes to half an hour to warm up to full brightness. CCFL backlit displays include the Apple Cinema Display (20-inch DVI), (23-inch DVI), and (30-inch DVI).

Newer displays use LED (Light Emitting Diode) backlighting that achieves full brightness and color saturation almost immediately. An example of an LED backlit display is the Apple Thunderbolt Display (27-inch).

Third-party display software

If the display works only when the Mac is started in safe mode, check for third-party software that might control how a display behaves. For example, use Spotlight, or open System Information and look under the Applications category to search for items like these:

• AirDisplay

• AirParrot

• DisplayLink

• DisplayPad

• iScreen

• Splashtop

• SwitchRes

If display-related software is installed, temporarily uninstall it to see if it resolves the issue. If so, refer the customer to the software's developer for possible updates.

Moving windowserver preferences

In some cases, the steps in the public section of this article might not resolve the issue. Moving the preferences files for the windowserver process can sometimes help. To remove these preferences, go to the correct folder (listed below) and move the files to the Trash ("XXXXXX" in the example represents a variable string of letters and numbers).

• /Library/Preferences/com.apple.windowserver.plist

• ~/Library/Preferences/ByHost/com.apple.windowserver.XXXXX.plist

After moving these files to the Trash, shut down the computer. Then, start up the computer and reset NVRAM.

Apple display adapters and firmware

Some video adapters have updates available that require special actions. Review the specific requirements for these adapters before performing further troubleshooting:

• Mini DisplayPort to VGA adapter

• Check the Graphics and Displays sections of System Information for the Mini DisplayPort to VGA adapter firmware version.  If the firmware version is earlier than 1.03, install the Mini DisplayPort to VGA Firmware Update.

• The Mini DisplayPort to VGA Adapter must be plugged into the Mac and a compatible VGA display. If the Apple computer is a notebook, the MagSafe power adapter must be plugged into a power outlet.

• Mini DisplayPort to DVI adapter

• This is the Single Link (maxiumum resolution 1920 x 1200) DVI adapter.

• This adapter does not show a version number because there is no firmware on this adapter.

• Mini DisplayPort to Dual-Link DVI adapter

• OS X v10.5.7 or later is required to use this adapter.

• Check the Graphics and Displays sections of System Information for the Mini DisplayPort to DVI (dual-link) adapter firmware version.  If the firmware version is 1.01 or 1.02, replace the customer's adapter. The new adapter should be firmware version 1.03 or later.

Adapters not made by Apple

Third-party companies also make adapters that can be used with existing Apple adapters and displays to convert one connection type to another. Verify that the video port on the Mac and the Mac hardware are functioning normally. Verify that the version of macOS that is currently installed is supported on this Mac and up to date.

If the third-party adapter is sold on the Apple Store or otherwise recommended, and everything else is working properly, send a low priority RTA as you would for an Apple adapter with issues for review.

If the third-party adapter is not sold on the Apple Store, refer the customer to the adapter manufacturer for additional help.

Related internal articles

• About display and television compatibility issues

Escalating unresolved issues

If the steps in this article don't resolve your customer's issue, please gather the following information and send a low priority RTA:

1. The specific brand and model of each display involved.

2. A specific description of the symptom or issue reported by the customer.

3. Steps to reproduce the behavior.

4. Note how the displays are connected to the computer, including any adapters, switch boxes, extension cables, etc. that are in use (exact makes and models).

5. If the issue happened after installing a specific update or app, please note which updates or apps were applied.

6. If there are other computers that you tested with the same display(s), include information on the make, model, and configuration of each.

7. Try to capture a screenshot of the issue. If the screenshot doesn't exhibit the issue when viewed on another computer (like your Mac), note this in your RTA. This helps to determine where the issue is happening.

8. If the issue can't be captured by a screenshot, see if the customer can provide a photo taken from a mobile phone or other device.

9. Include a full Capture Data report and Timing Snoop with the display connected to the Mac if possible.

Note that there is limited graphics performance when the Mac is started from safe mode or OS X Recovery. Some issues might not happen when the Mac is started up in these modes.

Information about products not manufactured by Apple, or independent websites not controlled or tested by Apple, is provided without recommendation or endorsement. Apple assumes no responsibility with regard to the selection, performance, or use of third-party websites or products. Apple makes no representations regarding third-party website accuracy or reliability. Risks are inherent in the use of the Internet. Contact the vendor for additional information. Other company and product names may be trademarks of their respective owners.

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Article: 

HT201177

Last Modified: 

02/24/2017

Radar Number: 

21880821, 27793878, 29140227 View >

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