MacBook display flickering, lines or coloured bands — diagnosis

A flickering or lined MacBook screen panics people. But the specific pattern of the fault tells you exactly what's wrong — and some of these are cheap fixes, not whole-logic-board replacements. Here's what to look for.

1. Flickering that goes away at specific angles (Flexgate)

If opening the lid past about 40° causes the screen to flicker, go dark, or develop a "stage light" effect (dark patches at the bottom), you have Flexgate — a well-known design flaw on MacBook Pro 2016-2018 models. The display flex cable is too short and wears through where it wraps around the backlight fixture every time the lid opens and closes.

Identifying Flexgate:

• Affects MacBook Pro 13-inch and 15-inch, 2016 to 2018 (the 2019 models fixed it with a longer cable).
• Flickering disappears when lid is at ~30° open, reappears past ~60°.
• May present as "stage light" darkness at the bottom of the display.
• Eventually the backlight dies completely.

Apple ran a free repair program for the 13-inch 2016 model only. Program ended around 2022. Everyone else has to pay.

Fix: replace the display flex cable. The cable is a £15-30 part, 90 minutes of labour. Third-party repair: £90-140. Apple's approach is to replace the whole display assembly (£600+). Avoid Apple for this one.

2. Vertical or horizontal lines across the whole screen

Thin, coloured lines running top-to-bottom or side-to-side usually mean LCD panel damage — either physical impact or a failed panel driver.

• Lines in fixed position every boot, same colours: damaged panel.
• Lines that change position / flicker / come and go: loose display cable or failing GPU.

Fix:

• Panel replacement: £180-350 depending on model. Genuine-spec panels from iFixit or authorised parts suppliers.
• Cable reseat: £40-80 if the cable is OK and just needs reseating.

3. Coloured bands that shift when you move the screen

Blotches of magenta, green or cyan across the image, particularly when the lid is flexed or you tap the bezel, mean the display connector has pulled partway out.

• Open and close the lid slowly — do the bands change?
• Gently flex the lid — do they shift?
• If yes, the connector (inside the hinge or at the logic board) has worked loose.

Fix: open and reseat the connector. £40-80. Not a big repair, but needs the bottom case off and done carefully.

4. Flickering during heavy GPU tasks only

If the display is fine during normal use but flickers or glitches only when gaming, editing video, or doing other GPU-heavy work, you have a failing graphics card. This is almost exclusively an Intel MacBook Pro 15-inch 2016-2019 problem — the AMD Radeon dGPU on those models has a well-documented failure rate.

Symptoms:

• Flicker during Photoshop / Final Cut / any game.
• Eventually random kernel panics.
• Eventually won't boot at all ("folder with question mark").

Fix: in most cases, the logic board has to be replaced because the GPU is soldered on. That's £400-700 in third-party repair, £1200+ at Apple. On older models this often isn't economic.

A workaround exists: gfxCardStatus app lets you force the MacBook to use only the integrated Intel GPU and ignore the failing dedicated one. Runs cooler, no 3D games or video editing — but the machine stays usable for browsing and document work. Extends the life of an otherwise-dying 2017 MacBook Pro by years.

5. Flickering that covers the whole screen at random

Random whole-screen flicker, sometimes once a minute, sometimes constant, without any specific trigger, is usually the display cable (flex) failing. Same cable as Flexgate (section 1) but at a different wear stage.

Fix: cable replacement, £40-100 fitted.

6. "Rainbow" test-pattern flashing on boot

If you see multi-coloured test patterns or a rainbow effect during boot only, clearing after a few seconds, that's normal GPU handshake with the panel. Not a fault.

If it persists past the login screen, the GPU or display driver is not successfully initialising — usually a logic board fault.

What to try before sending it in

• Force reboot (hold power 10s): clears software display glitches.
• Reset NVRAM (Intel): clears corrupted display settings.
• External display test: if the external shows a perfect image, your issue is display-side only. If the external also shows the same artefacts, the GPU or logic board is at fault.
• Adjust lid angle: confirms or rules out Flexgate.

When to send it in

If you've identified the pattern but aren't up for opening the laptop yourself, we do all of these repairs: Flexgate cable, display panel, connector reseat, and in some cases GPU board swaps. Send it in and we'll identify the specific fault, quote it, and repair. Free diagnosis, no-fix-no-fee, 90-day warranty.