You open your MacBook Pro and there they are. Thin horizontal lines cutting across the screen — steady, flickering, or appearing only at certain angles. Maybe one line. Maybe a cluster of them near the bottom. The machine is otherwise working perfectly. Before you assume the worst, there’s one test that will tell you almost everything you need to know.
Horizontal lines on a MacBook Pro display are one of the more common faults we see at Fixfactor — and one of the most frequently misdiagnosed, both by customers who assume the worst and by shops that jump straight to quoting a full screen replacement without investigating the root cause. The right diagnosis matters, because the root cause determines the repair, the cost, and the prognosis.
This guide walks through the main causes of horizontal lines on a MacBook Pro screen, how to work out which one you’re dealing with, and what the realistic fix looks like for each.
The One Test That Narrows It Down Immediately
Before calling anyone or forming any conclusions, do this: connect your MacBook Pro to an external display. Any monitor or TV with an HDMI or USB-C input will do. If you don’t have a cable at home, most libraries and some cafés have monitors available, and any Apple Store or repair shop can run this test for you in minutes.
The result of this test splits the universe of possible causes into two completely separate categories:
External display is clean — no lines
The fault is in the display assembly or the cable connecting it to the logic board. The graphics hardware inside the machine is working correctly — it’s the screen itself, or the connection to it, that has failed. This is the more common scenario, and generally the more repairable one.
Lines appear on the external display too
The fault is before the display — in the GPU, the display controller on the logic board, or the logic board itself. This is a more serious fault that requires component-level diagnosis. The display assembly itself may be entirely fine.
This single test determines the entire direction of the diagnosis. Run it before spending money on anything else.
If the External Display Is Fine: The Display Cable Problem
This is the most common cause of horizontal lines on MacBook Pro screens, and it has an origin story that Apple would probably prefer people forget.
The display cable — the ribbon cable that carries video signal and power from the logic board through the hinge assembly to the display panel — is routed through a very tight bend radius in thin MacBook Pro models. On older and thicker machines, this cable had plenty of room. On the redesigned MacBook Pro models from 2016 onwards, Apple made the machines significantly thinner, and the display cable routing became extremely tight. The cable flexes every time you open or close the lid.
Over hundreds or thousands of open-close cycles, this repeated flexing causes the cable to develop micro-fractures — tiny breaks in the conductors inside the cable that are invisible to the naked eye. The result is intermittent signal loss on some of the horizontal pixel lines that the damaged conductors were responsible for driving. You see this as horizontal lines on the screen.
If the lines on your screen change, appear, or disappear depending on the angle you hold the lid, this is a strong indicator of a display cable fault. The cable is under different tension at different angles — when you find the angle where the micro-fractures just barely maintain contact, the lines reduce or disappear. When the angle increases the strain on the cable, they worsen.
A screen where lines are static and completely unchanged regardless of lid angle is less likely to be a cable fault and more likely to be panel damage or a logic board issue.
Which MacBook Pro models are most affected
The display cable fault is heavily associated with the MacBook Pro models produced between 2016 and 2019 — the “thin” redesign generation that introduced the Touch Bar. The 13-inch models from this generation are particularly prone to it, though the 15-inch models are not immune. These machines are now between five and nine years old, which means they’ve accumulated a significant number of lid cycles, and the cable failures are appearing in volume.
MacBook Pro models from 2020 onwards use a redesigned cable routing with a longer cable and a less severe bend radius. Horizontal line faults on these models do occur, but the cable-fatigue mechanism is significantly less common. When lines appear on newer machines, a different cause is more likely.
The repair: cable replacement vs full assembly
The good news is that on many affected models, the display cable can be replaced as a standalone component — without replacing the entire display assembly. This is a meaningfully less expensive repair than a full screen replacement. The cable itself is not an expensive part; the cost is in the careful labour required to access and replace it without disturbing the panel, the antenna array, or the hinge mechanism.
A reputable repairer will assess whether the panel itself has been damaged by the faulty cable before recommending cable-only replacement. In most cases where lines appeared gradually, the panel is intact and cable replacement resolves the issue completely. Where the fault has been allowed to worsen significantly over time, the panel may have sustained secondary damage and the full assembly may be needed.
Every time you open and close the lid, you flex the cable further. A fault that starts as one or two faint lines at the bottom of the screen can progress to a large band of dead pixels or a completely black screen if the machine continues to be used normally for weeks. If you’ve identified that lines change with lid angle, the kindest thing you can do for the repair prognosis — and your wallet — is to stop cycling the lid and get it looked at promptly.
If Lines Appear on the External Display Too: A Logic Board Fault
When horizontal lines reproduce on an external monitor, the fault is in the hardware that generates the video signal — the GPU, the display controller, or their associated circuitry on the logic board. The display assembly itself is not the problem.
This is a more serious diagnosis, but it doesn’t automatically mean the machine is beyond repair. The outcome depends heavily on the specific fault and the model.
GPU failure on older models
The MacBook Pro 2011 models — both 13-inch and 15-inch — suffered from a well-documented GPU failure issue caused by weak solder joints under the discrete graphics chip. As the machine heats and cools through normal use over years, the solder fatigues and eventually loses contact. The symptom is horizontal lines, graphical artefacts, or a black screen — and because it’s the GPU itself, the external display shows the same problem. Apple ran an extended warranty programme for this, which has long since expired. These machines are now old enough that the repair economics are difficult, and component-level reballing of the GPU — while technically possible — must be weighed carefully against the machine’s remaining useful life.
Logic board component failures on newer models
On more recent MacBook Pros, GPU-side horizontal lines are typically caused by a component failure on the logic board rather than the GPU die itself — a failed voltage regulator, a damaged display controller, or a solder joint issue on the board traces that carry display signals. These are component-level faults that require microsoldering diagnostics to identify and address.
Unlike a cable replacement or screen swap, logic board repair for GPU-side display faults requires a technician to trace the signal path under magnification, identify the specific failed component, and replace or rework it. This is more time-intensive than most other laptop repairs, and not all repair shops have the equipment or expertise to do it. Many will quote a full logic board replacement instead — which is significantly more expensive and often unnecessary when the fault is a single component.
If you’ve been quoted a full logic board replacement for horizontal lines on a MacBook Pro, it is worth seeking a second opinion from a shop that offers component-level microsoldering diagnostics before agreeing to that cost.
Physical Damage to the Panel Itself
A third cause of horizontal lines — usually more obvious — is direct physical damage to the LCD or LED panel. A knock, a drop, pressure applied to the closed lid, or an object trapped between the keyboard and screen when the lid was closed can all crack or stress the panel internally in ways that aren’t always visible from the outside as a crack, but manifest as lines, blotches, or bands of colour.
Panel damage is typically distinguishable from cable or logic board faults by a few characteristics: the lines are static regardless of lid angle, they may be accompanied by irregular patches of discolouration or visible pressure marks, and the external display test will show a clean image. The repair in this case is a display assembly replacement.
The assumption that horizontal lines automatically require a full screen replacement — which is often the first quote people receive — is frequently wrong. In the most common scenario (display cable fault on 2016–2019 models), the panel is entirely intact and only the cable needs replacing. In the GPU-fault scenario, the screen is entirely fine and replacing it would change nothing. A proper diagnosis before any repair work begins is not optional — it’s the entire basis for recommending the right fix.
Software Steps Worth Trying Before Anything Else
In a small number of cases, display anomalies on MacBooks have a software or firmware origin rather than a hardware one. These are much rarer than hardware faults, but they cost nothing to attempt and take under five minutes. Try these first — particularly if the lines appeared suddenly after a macOS update or after the machine woke from sleep.
- Restart the machine. Straightforward, but occasionally resolves display artefacts caused by a graphics driver hanging in a bad state after sleep or an update.
- Reset the NVRAM / PRAM. Shut down the machine. Power it on and immediately hold Option + Command + P + R for about 20 seconds until you hear the startup chime twice (or see the Apple logo appear and disappear twice on newer models). NVRAM stores display-related settings and a reset occasionally clears persistent visual faults.
- Reset the SMC. On MacBooks with a T2 chip (2018 and later): shut down, hold the power button for ten seconds, release, then start normally. On older MacBooks: shut down, hold Shift + Control + Option + Power simultaneously for ten seconds, then start normally. The SMC controls power delivery to the display backlight and related hardware.
- Boot into macOS Recovery. Hold Command + R on startup. If the lines are absent in Recovery mode (which uses basic graphics drivers), the fault is software or driver-related rather than hardware. If lines persist in Recovery, the fault is hardware.
If none of these steps change anything, the fault is almost certainly hardware. Move on to the external monitor test and arrange a professional diagnostic.
Practical Recommendations
- Run the external monitor test before calling anyone.It takes five minutes and immediately tells you whether you’re dealing with a display-side fault or a logic board fault. This single piece of information is worth knowing before you speak to any repairer, because it determines everything about the conversation that follows.
- If lines change with lid angle, stop cycling the lid.Continued use accelerates cable degradation. If the angle test suggests a cable fault, keep the machine at a fixed working angle until it can be inspected. Each additional opening-closing cycle risks converting a cable replacement into a full assembly replacement.
- Check your Apple repair programme eligibility first.If you have a 2016 or 2017 MacBook Pro, verify with Apple whether your serial number is still eligible for any repair programme coverage before paying for a repair out of pocket. Apple’s support website has a serial number checker for active programmes.
- Don’t accept a “new screen” quote without a proper diagnosis.Horizontal lines are frequently quoted as a screen replacement without investigation. If a repairer quotes you for a full display assembly without first performing the external monitor test, asking about the angle behaviour, or offering a diagnostic — get a second opinion. The correct repair may be significantly less expensive.
- For logic board faults, seek a component-level repairer.If the external display confirms a GPU or logic board fault, a repairer who offers only whole-assembly swaps will quote you far more than necessary. A shop with microsoldering capability can often isolate and fix the specific failed component rather than replacing the entire board.
- Act sooner rather than later on intermittent faults.Intermittent lines — faults that come and go — typically indicate a problem in its early stages. A cable that’s partially failing, a solder joint under stress, a component running at the edge of its tolerance. Early intervention is almost always cheaper than waiting for the fault to progress to a complete failure.
MacBook Pro Lines on Screen? Let’s Diagnose It Properly.
Bring your MacBook Pro in and we’ll run through the full diagnostic process — external display test, angle assessment, software checks — and tell you exactly what’s causing the problem before recommending any repair.
We carry display cables and assemblies for a wide range of MacBook Pro models, and we offer component-level microsoldering for logic board faults that other shops quote as full board replacements.
