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MacBook Pro black lines bottom screen: what to check first

By Alberto Gulotta · Updated 9 October 2026 · 10 min read

MacBook Pro black lines bottom screen: before paying for a display, run two checks. Take a screenshot with Shift-Command-3 and look at it on another device: in our reading, lines missing from the picture point at the display. Then run Apple Diagnostics, which from macOS Tahoe 26 lets you choose a test for the built-in display.

1. Take a screenshot while the lines show. Apple’s shortcut for the whole screen is Shift, Command and 3 pressed together; Apple says the screenshot saves to the desktop, unless you have changed where screenshots go.
2. Look at it on another screen. Send it to a phone, or open it on another computer. If the lines aren’t in the picture, they are not in what the Mac is drawing: that reasoning is ours, set out below.
3. Shut down and disconnect accessories. For Apple Diagnostics, Apple says to keep only keyboard, mouse, display, Ethernet and power connected, with the Mac on a hard, flat, stable surface with good ventilation.
4. Start Apple Diagnostics. On a Mac with Apple silicon, hold the power button, release it when Options appears, then hold Command-D until the Mac restarts. On an Intel Mac, hold D as it starts, or Option-D if D doesn’t work.
5. Choose a test, and keep any code. Apple says that in macOS Tahoe 26 and later you choose a diagnostic, such as the one for the built-in display; earlier versions run automatically. If you see reference codes, Apple says to give them to the Apple Store, Authorized Service Provider or Independent Repair Provider that repairs the Mac.

What one poster tried. In the same thread, the poster with the MacBook Air wrote that a software update and a PRAM and SMC reset did not remove the lines. On an Intel-based Mac, Apple lists Option-Command-P-R at startup to reset NVRAM or PRAM, and Shift to start in safe mode; on a Mac with Apple silicon, startup options come from holding the power button. What safe mode can and can’t prove is in safe mode.

What Apple’s display page says. Its Mac User Guide page for display problems, in the version for macOS Ventura 13, says to check that Mac and display are connected with good quality cables and adapters if the display flickers, that interference from nearby electrical devices may also cause it, and that bright or dark spots may be pixel anomalies; for a high number of anomalies, or an Apple display whose problem can’t be corrected, it says to contact Apple or an Apple Authorized Service Provider, and warns that repairs by untrained people or with non-genuine parts may affect safety and function. Single dots rather than lines are in dead pixel repair on a laptop.

What posters report. In the Apple Community thread, several people wrote that the lines went away with the lid tilted towards the keyboard, at about 45 degrees. Two wrote that an authorised service centre told them the whole display had to be replaced because the cable is not replaced on its own. These are reports from users, not Apple statements. A vertical line on a laptop of another make is in a vertical black line on a laptop screen.

The repair. Apple’s repair page for Mac laptops says the final fee is set after inspection, that its estimates are for out-of-warranty service and may be subject to tax, and that Authorized Service Providers can set their own fees. The Apple Limited Warranty covers manufacturing issues for one year and not accidental damage, in addition to consumer law where you live. Backing up is in backing up a MacBook.

Not covered here. It does not cover opening a MacBook Pro, replacing the display yourself, or faults of external displays connected to a Mac.