How to Test a Phone Screen for Dead Pixels
Last updated: August 2026
Why check for dead pixels?
Dead pixels and stuck pixels are small display defects where a single pixel does not display the correct color. They can appear on new devices as manufacturing defects or develop over time on older screens. Finding them early matters — especially when buying a used phone or checking a device under warranty.
What you need
- The phone or tablet you want to test
- A modern web browser (Chrome, Safari, Edge, or Firefox)
- A few minutes of time
No app installation is required. The test runs entirely in your browser.
Step 1: Open the screen test
Open the Screen Test page on your phone. The test is designed to work on any modern mobile browser.
Step 2: Enter fullscreen
Tap the fullscreen button to hide the browser interface. This gives you an unobstructed view of the entire display, making it easier to inspect edges and corners where defects often appear.
Step 3: Inspect each color
The test cycles through solid colors — white, red, green, blue, and black. On each screen, carefully look for:
- Black dots on white — these are dead pixels (permanently off)
- Colored dots that do not change — these are stuck pixels (permanently lit in one color)
- Dim or discolored areas — may indicate pressure damage or backlight unevenness
Step 4: Check edges and corners
Pay special attention to the edges and corners of the screen. Dead pixels are sometimes hidden near the bezel where they are harder to notice during normal use.
Step 5: Note what you find
If you find any defective pixels, note their approximate position on the screen. This information is useful when contacting the manufacturer about a warranty claim.
What to do next
If you find dead or stuck pixels on a device under warranty, contact the manufacturer. Most have a threshold (typically 3–5 dead pixels) before they consider it a defect covered by warranty. For used devices, this information helps you assess the screen condition before purchasing.