Guide · Updated October 16, 2026
MacBook screen lines or flickering: what to check first
Lines across the picture, flicker, a glowing bottom edge or a screen that blacks out at a certain lid angle. Before you assume the worst, two quick tests tell you whether the problem is the screen itself or something behind it.
1. The screenshot test
Press Shift + Command + 3 to take a screenshot while the lines or flicker are visible, then open it on another device — your phone, or another computer.
- The lines are in the screenshot: the image is being drawn wrongly before it reaches the panel. That points to software or to the graphics hardware on the logic board.
- The screenshot looks clean: the Mac is producing a correct picture and the problem is in the display or its cable.
2. The external display test
Connect a monitor or TV. If the external picture is perfect while the built-in screen is not, the display assembly or its cable is at fault. If the external picture shows the same lines, look at software and the logic board instead.
Software checks worth trying
- Update macOS in System Settings → General → Software Update. Display bugs do get fixed.
- Start up in Safe Mode. On an Apple silicon Mac, shut down, hold the power button until startup options appear, select your disk, then hold Shift and choose Continue in Safe Mode. On an Intel Mac, hold Shift as it starts. If the flicker stops, a login item or app is likely involved.
- Check brightness settings. In System Settings → Displays, turn off automatic brightness and True Tone for a day. Brightness that pumps up and down can look like flicker.
- On a 14- or 16-inch MacBook Pro, try changing the refresh rate in System Settings → Displays from ProMotion to a fixed rate, to rule out a software interaction.
Hardware patterns to recognise
| What you see | What it usually is |
|---|---|
| Fine vertical or horizontal lines that appeared after the lid was squeezed, sat on or closed on something | Damage to the panel or its internal connections. The display assembly needs replacing. |
| Dark, ink-like patches that spread over days | A cracked panel leaking liquid crystal inside. It will not recover. |
| A glow like stage lights along the bottom edge, or a picture that cuts out once the lid opens past a certain angle | A worn display flex cable — a well-known weakness of 2016 and 2017 MacBook Pro models. Apple ran a backlight service program for some 2016 13-inch models; it has since ended. |
| Lines or flicker that change when you press gently near the hinge | A loose or damaged display cable connection. |
When to stop troubleshooting
If the screenshot is clean, the external display is fine, and you can see any of the patterns above, more settings changes will not help: the screen or its cable needs repair. Back up while you still can — an external display makes that easy even if the built-in screen is unreadable.
For what the repair involves and why it is usually a full display assembly, see MacBook screen replacement. Or call with your model number and we will tell you whether the part is in stock.