Foldable Screen Test

How to use

1. Open the phone flat and go full screen. Unfold it all the way and tap Full screen under the sweep area, so it covers the whole inner screen.
2. Drag one finger across the fold. Start on one half and slide slowly to the other without lifting. On a Z Fold or Pixel Fold that means left to right. On a Z Flip the fold runs across the screen, so drag from top to bottom.
3. Lift and read the verdict. The verdict appears when your finger leaves the glass. Clean sweep means the screen followed you the whole way. Anything else puts a red circle on the spot where it lost you.
4. Cover the whole fold. Repeat near both ends and the middle of the crease. Film trouble usually starts at the bottom end, so give that end an extra pass.
5. Check the crease on gray. In Crease visibility, go full screen and step through white and the three grays. Look at the fold at an angle, under a light.

Why test this

On a foldable phone, the screen usually fails at the fold first. The inner panel bends there every time you open it, so the touch layer and the image along that strip take the most wear. It rarely goes all at once. A swipe stalls halfway across. The keys in the middle of the keyboard need a second tap. A scroll jumps as it passes the center. A thin line shows up and stays. This page checks three things from the browser: whether touch keeps up across the crease, whether the image along it is clean, and what the phone reports about its own fold. Run it on a used Galaxy Z Fold, Z Flip or Pixel Fold before you pay. Run it after a screen repair to confirm the new panel tracks at the fold, or before a warranty claim so you can point at the exact spot. A browser can't see inside the phone, so it can't tell you why a strip failed or how long the screen will last. It can show you where the problem is, in about a minute, with nothing to install.

What the results mean

The verdict comes up when you lift your finger. Clean sweep means the screen reported your finger the whole way across. Slow spot means the screen went quiet for a short stretch while your finger kept moving. Dead gap means it went quiet for a long one, so a real strip of the fold reported nothing. Touch lost means the screen let go of your finger and picked it up again as a new touch, the classic dead strip at a fold. Too short means the drag didn't cover enough ground to judge. The red circle marks the worst spot. Biggest gap is how far your finger moved without a report. Gap time is how long that took. Normal step is the usual distance between two reports on this screen. A gap only counts when it is long in both distance and time, so resting your finger on the fold is not a fault. One bad result can be a dry fingertip or a lifted edge of the film. A miss in the same place on every pass is the panel. If misses appear only while charging, unplug and run it again. On the grays, a crease you see only at an angle is normal. A line that stays dark or bright on every gray is not.

FAQ

Is a visible crease a defect?

No. Every folding screen has a crease. On most models you can see it at an angle and feel it under a fingertip. It becomes a problem when touch fails along it, a dark or bright line shows up on the gray fills, or the screen film bubbles and lifts.

How do I know if the crease is not registering touch?

Drag one finger slowly across the fold and lift. Dead gap or Touch lost means the screen missed your finger on the way over, and the red circle shows where. Get the same result in the same place three times and it's the panel, not your finger.

What is the difference between Slow spot and Dead gap?

Both mean the screen stopped reporting your finger for a moment while it kept moving. A slow spot is a short pause, the kind a dry fingertip can cause. A dead gap lasts long enough that the strip under it isn't tracking. Treat a dead gap as a fault, and recheck a slow spot a few times before you decide.

What does a black line down the middle of my inner screen mean?

A thin line that stays in the same place on every gray usually means damage inside the panel at the fold, such as a cracked layer or debris pressing on it from behind. It's not a software bug. Fold the phone gently and get it looked at before the line spreads.

Can a screen protector cause a dead strip at the fold?

Yes. The film on the inner screen can bubble or lift along the crease, most often at the bottom end, and a lifted edge can swallow touches. Look at the fold under a light at an angle before you blame the panel. Don't peel the film off yourself. Samsung warns that a removed or non-official film can cause touch problems, and a service center replaces it.

Why don't I see the dashed crease line?

The line appears only in full screen, and only when your browser reports the screen as two halves. Recent versions of Chrome and Samsung Internet do that while the phone is partly folded. Flat, the phone reports one screen, so there's no line to draw. The drag test works the same either way.

Does this work on the iPhone Duo?

We haven't run it on an iPhone Duo yet, so we can't promise how it behaves there. The drag test needs only touch, which Safari supports like any other browser. Safari doesn't support the Device Posture or Viewport Segments APIs, so on an iPhone the Posture panel can only watch for the jump in screen size when you open or close the phone.

Should I run this before buying a used foldable?

Yes. Open the seller's phone, load this page, and drag across the full length of the crease, then step through the grays. It takes about a minute and checks the fault most likely to cost you a new inner screen.