A black line on your Mac screen appears as a thin dark stripe running horizontally or vertically across the display. This guide covers black lines on MacBook, MacBook Air, MacBook Pro, and iMac models, explaining the causes, diagnosis methods, and repair options.

Black Line on Mac Screen: Why It Appears and How to Fix It

What Is a Black Line on a Mac Screen

A black line on a Mac screen is a visual defect where one or more rows (horizontal line) or columns (vertical line) of pixels display permanently dark. Unlike temporary screen artifacts, a true black line is a hardware failure where those specific pixels no longer receive or process video signals.

On Mac laptops, black lines almost always originate from one of three causes: flex cable failure at the hinge, display panel dead pixel row failure, or GPU-related issues. On iMac and external displays, black lines are more likely to originate from GPU or display panel issues.

Identifying which component is causing the line is the first step to finding the right fix.

Most Common Causes of Black Lines on Mac Screens

Flex Cable Failure at the Hinge (MacBook Models)

The MacBook's display connects to the logic board through a flex cable that passes through the hinge. This cable carries video signals and handles the constant bending from opening and closing the lid.

MacBook models from 2016-2019 (with the butterfly keyboard design) are particularly susceptible to flex cable issues because:

• The cable had to route through a narrow space around the butterfly keyboard mechanism
• Multiple bends and tight routing stressed the internal traces
• Over time, the copper traces developed micro-cracks at bend points

Apple acknowledged this issue in several repair programs. However, even newer MacBook models with improved cable designs can develop flex cable problems from heavy daily use.

Signs of flex cable failure:

• Line changes intensity or position when lid angle changes
• Line may flicker or disappear at certain angles
• The issue may come and go before becoming permanent
• On MacBook Pro 2016-2019, may be accompanied by other issues (ghost images, screen flickering)

Display Panel Dead Pixel Row

The LCD or OLED panel itself can develop dead pixel rows. When the pixel circuits for an entire row fail, that row displays as a permanent black line.

Panel failure signs:

• Line stays in exactly the same position always
• Line does not change regardless of lid movement
• Line is visible on all background colors
• No flickering or intermittent behavior
• May have appeared after a drop or impact

GPU Issues (Certain MacBook Pro Models)

Certain MacBook Pro models have known GPU issues that can cause black lines:

• MacBook Pro 2016-2019 with Touch Bar: Some models experienced GPU failures that caused display artifacts including lines
• MacBook Pro 13 and 16-inch 2020 (Intel): Some units with the AMD Radeon Pro 5600M had GPU issues
• iMac with AMD GPUs: GPU failures can cause lines on iMac displays

Signs of GPU-related lines:

• Lines appear on external monitors connected to the Mac
• Other visual artifacts appear (color distortion, flickering)
• System may crash or freeze during GPU-intensive tasks
• Lines may appear alongside other symptoms

Physical Impact Damage

Dropping or pressing on a MacBook can damage the display internally, creating black lines even if the glass shows no cracks. Impact damage typically causes immediate, permanent lines that do not change over time.

How to Diagnose a Black Line on a Mac

Step 1: The Lid Angle Test

For MacBook and MacBook Air/Pro:

1. Open the laptop to a normal viewing angle
2. Observe the black line carefully
3. Gently change the lid angle through its range
4. Watch whether the line changes

• Line changes: Flex cable failure (most common)
• Line stays stable: Panel dead pixel row

Step 2: The External Display Test

1. Connect an external monitor via USB-C/Thunderbolt or HDMI
2. Observe whether the same line appears on the external display
3. Also test with the lid closed (clamshell mode)

• Line on external monitor: GPU or software issue
• No line on external monitor: Display panel or flex cable

Step 3: Check for Known Issues

1. Visit support.apple.com
2. Enter your Mac's serial number (Apple menu > About This Mac > Overview > Serial Number)
3. Check for any active repair programs

Step 4: Safe Mode Test

1. Restart the Mac and hold Shift during startup
2. Wait for Safe Mode to load
3. Observe whether the line appears in Safe Mode

If the line does not appear in Safe Mode, a software or driver issue is possible.

Step 5: Identify Your Mac Model

• MacBook Pro 2016-2019: Known flex cable issues, GPU issues on some models
• MacBook Air 2017-2019: Flex cable routing concerns
• MacBook Pro 2020+ (Apple Silicon): More robust design
• MacBook Air 2020+ (Apple Silicon): Improved reliability
• iMac: Line issues more likely GPU-related

How to Fix a Black Line on a Mac

Fix 1: Check for Apple Repair Programs

Before paying for any repair:

1. Go to support.apple.com
2. Enter your serial number
3. Review active programs
4. If eligible, Apple may repair or replace at no cost

Apple's repair programs have covered specific MacBook Pro models for display issues, GPU issues, and backlight issues.

Fix 2: Update macOS and Reset NVRAM

Rule out software causes:

1. Go to System Settings > General > Software Update
2. Install all available updates
3. Reset NVRAM: shut down, then power on and immediately hold Option + Command + P + R for about 20 seconds

Fix 3: Flex Cable Reseating (Third-Party Repair)

If the line changes with lid angle:

1. A professional repair shop can open the MacBook
2. Reseat or replace the display flex cable
3. Cost: $80-150 for parts and labor

Note: MacBooks are notoriously difficult to open without damaging components. This repair should only be attempted by experienced technicians.

Fix 4: Screen Replacement

For panel failures:

• Apple / Apple Authorized Service Provider: $400-800 depending on model
• Third-party repair shops: $200-500 for genuine or high-quality aftermarket panels

For MacBook Pro with Retina display, the screen and glass are fused together as one assembly, increasing replacement costs.

Fix 5: GPU Repair/Replacement

If GPU is confirmed as the cause:

• GPU repair on iMac: $200-400
• Logic board replacement: $400-800+
• For covered MacBook Pro models: may be free under repair programs

When Hardware Repair Is Needed

Seek professional repair when the line appeared after physical impact, the line is stable and permanent regardless of lid movement, the line appears on external monitors too, the Mac is covered by an Apple repair program, or the Mac is under AppleCare+ warranty.

AppleCare+ covers mechanical defects and accidental damage for Macs.

Prevention Tips for Mac Displays

• Open and close the MacBook lid by gripping both sides
• Avoid placing objects on the keyboard and closing the lid
• Use a protective case or sleeve when traveling
• Consider using an external keyboard and monitor for stationary desk use
• Keep the MacBook away from magnets (can affect display calibration)

Related Guides

• Mac Screen Issues: Yellow tint and other Mac display issues
• Orange Screen on MacBook: Orange discoloration on Mac screens
• Dead Pixel Diagnosis: Distinguish dead pixels from black lines
• Screen Flickering on MacBook: Related Mac screen flickering issues
• Screen Test Tool: Free tool to test your Mac display

Conclusion

A black line on a Mac screen is most commonly caused by flex cable failure at the hinge on MacBook models, followed by display panel dead pixel rows. MacBook Pro models from 2016-2019 are the most affected by cable issues, and some are covered under Apple's repair programs. The diagnostic tests — lid angle test, external monitor test, and serial number check for repair programs — quickly identify the cause and appropriate solution. Always check for Apple repair programs before paying for third-party repairs. For out-of-warranty repairs, third-party shops offer flex cable replacement for $80-150 and screen replacement for $200-500, compared to Apple's $400-800 screen replacement costs.