Screens · guide

White horizontal lines on phone screen: what they mean

By Alberto Gulotta · Updated 11 September 2026 · 16 min read

White horizontal lines on phone screen are treated as a hardware fault by the companies that make the phones, not as a glitch to reboot away. Google says so on its own support page, and offers a single software step before repair. Your phone also has a diagnostic built in that almost nobody opens.

That gap matters because of who is answering this question elsewhere. On the first page of results there is a page from a phone insurer that serves no readable text at all, a manufacturer of replacement panels whose article ends in a wholesale enquiry, a question behind a security check, and five years of forum answers. The summary at the top of the results lists “Software glitches” among the common causes and credits it to the insurer. Meanwhile the two documents read for this guide that name lines on a screen at all — Google’s Pixel support page and Lenovo’s damage guide — both file them under hardware.

Read the list of tests in your phone’s diagnostic before you read its verdict. Samsung’s published list covers NFC, the mobile network, proximity, buttons, speaker, camera, Bluetooth, face recognition, USB, wireless charging, SIM, sensors, touch screen, flashlight, vibration, mic, Wi-Fi, fingerprint, charging and battery status. It is a long list and it does not contain a colour test of the panel: “Touch screen” checks whether the glass answers your finger, which a phone with perfect touch and a white line across it will pass. A green tick on the wrong test is worse than no test, and this is the kind of detail the pages that recommend “run a diagnostic” never mention.

1. Take a photograph of the screen with another phone, today. Not of the picture on it — of the lines. Everything that happens next, from a warranty conversation to a repair quote to selling the phone, turns on whether the lines are spreading, and that is a comparison rather than an impression.
2. Install any pending system update. It is the one software step Google offers for this symptom — Settings, System, System update — and it is worth doing first precisely because it is the only one anybody official recommends.
3. Run the maker’s own diagnostic. Samsung Members, or Settings → Device care → Diagnostics on a Galaxy; the dial-pad code on a Pixel. Read what the tests are called: a touch test that passes says nothing about lines, and knowing that keeps you from taking a green tick as an answer.
4. Press nothing and rub nothing. The advice that circulates for marks on screens is to press or massage them; the maker of a laptop panel writes that “Applying pressure can crack the screen or damage internal components”, and a phone panel is thinner than a laptop one, not thicker.
5. Then ask for a price rather than a diagnosis. On a phone the screen is an assembly, and the question is not which part failed but what a replacement costs against what the phone is worth. Apple publishes an estimated cost per iPhone model for screen damage, and adds “We’ll inspect your device to determine the final service fee.” — so the published figure tells you the order of magnitude and the quote on your device decides.

About the phrase that follows this fault around: a flex cable. Repair sites will tell you the ribbon between the panel and the board has worked loose, and on a phone that has been dropped it is a perfectly reasonable guess. It stays a guess: none of the manufacturer pages read for this page name a cause at all, and the one maker vocabulary that puts names to display faults — Lenovo’s guide to damage it considers caused by the customer — is written for laptops, tablets and desktops rather than phones. It is worth reading anyway, because it shows how a manufacturer thinks about these marks: a vertical line has its own entry, “Vertical line appears when LCD is on”, and it sits in a list of things a standard warranty does not cover.

What that means in practice is that the useful question on a phone is rarely which component failed. The screen comes as an assembly; a repair is a swap; the decision is a price against the value of the phone and how long you meant to keep it. If the machine is old enough that the answer is no, the same money is often better spent elsewhere — and before you hand the phone to anybody, get a backup off it, because a screen repair means somebody else holding your device.

And if the fault is not lines but the touch that has stopped answering, or a screen that is dark rather than marked, this is the wrong page: a screen that ignores you has the four steps Apple publishes, and the entrance to the rest of these faults is computer screen problems.

Not covered here. It will not name the failed component. The manufacturer pages behind this page do not, and a confident guess about a ribbon cable would be somebody else’s guess repeated with more punctuation.

It will not walk you through a screen replacement. Google publishes repair manuals and prefaces them by saying that attempting a repair without the relevant technical skills risks injury or a broken device.

And it will not quote a price for your phone. Apple publishes an estimated cost per iPhone model and says the final fee follows an inspection; for an Android handset the figure depends on the maker and the repairer, and every other number in circulation comes from somebody selling the repair. What holds instead is simple: the statement that a screen which flickers, shows a green tint, or horizontal or vertical lines, will not turn on, or is cracked may have a hardware issue, the single software step of checking for and installing a system update, and the instruction to contact support or get the phone repaired if that does not resolve it, are quoted from Google’s article 16250690; the description of the Pixel Repair Diagnostics App as something to use before and after a repair, its availability on Pixel 3 and later and Pixel Tablet, and the instruction to open the Phone app, tap the dial pad and dial the diagnostics code, are quoted from Google’s article 14257407; the routes into Samsung’s diagnostics through the Members app and through Device care, the instruction to tap Test all for a full diagnostic, the note that Device care diagnostics are available on Galaxy devices running Android 12 or later, and the published list of tests including the touch screen test, are quoted from Samsung’s article ANS10003632; the safety instructions to discontinue use of an iPhone if damage to the phone or battery is suspected, not to use an iPhone with cracked glass, and that an iPhone battery should only be repaired by a trained technician, are quoted from Apple’s iPhone safety information; the statement that Apple inspects the device to determine the final service fee, published next to its estimated service cost table for iPhone screens, is from Apple’s iPhone screen repair page; and the entry describing a vertical line that appears when the LCD is on is quoted from Lenovo’s document HT104148, which is written for laptops, tablets and desktops rather than phones.