iPhone
A sudden vertical line after a drop is classic panel damage. Try an iOS update and a force restart first; Apple's pixel/line policy usually covers factory defects within warranty, not drop damage — AppleCare+ does.
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Why Is There a Line on My Screen?
A line appeared on your phone, laptop or TV and you want to know if it's serious. Start here: open each test color and watch the line. A line visible on every solid color is hardware — and that single observation tells you most of what you need to know.
Test in order: White → Black → Red → Green → Blue · Esc or tap exits
5 tests to find the cause
- 1
Photograph the line
Take a screenshot AND a photo of the screen. If the line shows in the photo but not the screenshot, the panel or cable is at fault — not the software.
- 2
Run the 5-color test
Open each full-screen color above. A line visible on every solid color — especially black and white — is a hardware fault in the panel or its connection.
- 3
Note the behavior
Is the line vertical or horizontal? Fixed or flickering? One pixel wide or a broad band? Each pattern points to a different cause below.
- 4
Rule out software
Restart the device, update the OS and graphics driver, and disable any recently installed overlay or theme app. Lines caused by software vanish after a restart.
- 5
Check the cable (external monitors)
Reseat or swap the HDMI/DisplayPort cable and try another port. Flickering lines that change when you wiggle the cable are a connection problem, not a panel fault.
What your line is telling you
Screens are drawn as a grid driven by row and column circuits. Where the line sits and how it behaves identifies which circuit — or which piece of software — is misbehaving:
| Line behavior | Most likely cause | What it means |
|---|---|---|
| Vertical line (top to bottom) | Usually a failing panel | One damaged column driver or a broken ribbon connection along the display edge. If it appears on every color in the test above, the panel needs service. |
| Horizontal line (side to side) | Panel or driver board | A damaged row driver. On laptops, open-and-close the lid gently — if the line flickers or moves, the display ribbon cable is worn and is cheaper to replace than the panel. |
| Flickering or intermittent line | Connection or GPU | Often a loose ribbon cable (phones, laptops) or an overheating GPU. If it also appears on an external monitor, suspect the graphics chip or driver, not the built-in screen. |
| Fixed line in the same spot, all apps | Hardware | Content-independent lines that survive restarts and show on solid test colors are physical defects. No setting will remove them. |
| Line only in one app | Software | A line that appears in a single app — but never on the solid test colors — is an app rendering bug. Update or reinstall that app. |
By device: iPhone, Samsung, laptop
Samsung & Android
Boot into safe mode: if the line disappears, a third-party app is drawing it. Samsung Members app has a built-in panel diagnostic. Green-tinted lines on AMOLED often follow pressure or heat damage.
Laptops (Windows/Mac)
Connect an external monitor: lines on both screens mean GPU/driver; lines only on the built-in screen mean panel or ribbon cable. Flex the lid gently to test the cable before buying a new panel.
Whatever the device, the decision path is the same: rule out software with a restart and update, rule out the cable with an external monitor or gentle lid flex, then let the 5-color test above deliver the verdict. Still seeing the line on solid colors after all that? It's the panel.
When to send it for repair
- The line shows on every solid test color — panel or ribbon fault. Repair is the only fix.
- The line is spreading or new lines keep appearing — a failing driver chain gets worse, not better.
- The device is under warranty and the line appeared without impact — document it with photos before the claim.
- External-monitor test was clean while the built-in screen shows lines — replace the panel or cable, not the GPU.
Repair economics: ribbon cables are cheap, phone AMOLED panels and laptop display assemblies are the expensive part. For devices older than ~4 years, compare the repair quote against a used replacement before committing. After any repair, re-run this test and the full monitor test before the warranty on the repair expires.
Lines on screen FAQ
Why is there a line on my screen?+
A line that shows on every color in a solid-screen test is hardware: a damaged row/column driver, a worn ribbon cable, or pressure damage to the panel. A line that vanishes on solid colors or after a restart is software — a driver, app or OS glitch.
Can a line on the screen go away on its own?+
Software lines disappear after a restart or update. Flickering cable-related lines may come and go when you move the lid, but true panel lines are permanent and usually spread slowly. Test monthly with the 5-color board above.
How do I know if it's the screen or the graphics card?+
On a laptop or desktop, plug in an external monitor. If the line also appears on the external screen, the GPU or driver is at fault. If the external screen is clean, the built-in panel or its cable is failing.
Is a vertical line covered by warranty?+
If the line appeared without drops or pressure and fails the solid-color test, most manufacturers treat it as a panel defect and replace it under warranty. A screenshot without the line plus a photo with it is strong evidence for your claim.
Can I fix a line on my screen myself?+
You can fix software causes: restart, update OS and drivers, reseat an external monitor cable. Panel and ribbon-cable faults require spare parts and are best left to a repair shop unless you have experience opening devices.