Screen Checker | Test Dead Pixels, Burn-in, Touchscreen Response and Refresh Rate (Hz)
Shows full-screen solid black, white, red, green, blue and gray, a gradient, black and white level steps, and a 1px checkerboard in turn, so you can check for dead pixels (stuck bright dots that stay lit and dark dots that never light), OLED burn-in, color non-uniformity, banding, and crushed blacks or blown-out whites. In the touch test, trace your finger over a grid covering the whole screen to see which spots stay unresponsive and how many points can be touched at once (multi-touch). The refresh rate test measures the browser’s frame interval for 3 seconds to tell whether the screen is running at 60Hz, 90Hz, 120Hz or 144Hz, and a moving square lets you compare smoothness. Includes a checklist for buying a used phone or monitor, checking for defects within the warranty period, or testing before selling secondhand, plus a copyable result.
Dead pixel & burn-in test screens
Fills the screen with solid colors, gradients and level steps. Tap (or click / press →) to go to the next color. The trick is to dim the room and look with your face close to the screen.
Bright dot (stuck on)
Find on black
Dark dot (dead pixel)
Find on white
Burn-in
Find on gray
To tell a dot apart from smudges or dust, gently wipe the screen, look again, and check whether the dot stays in the same place when the color changes. Methods that fix pixels by flashing the screen carry a risk for people with photosensitivity, so this tool doesn’t use them.
ABOUT
About Screen Checker | Test Dead Pixels, Burn-in, Touchscreen Response and Refresh Rate (Hz)
Screen Checker is a tool for checking a phone, tablet or computer monitor for screen problems using only your browser. No installation is needed. The dead pixel test fills the screen with solid black, white, red, green, blue, gray, cyan, magenta and yellow, a gradient, black and white level steps, and a 1px checkerboard in turn. On a black screen it’s easy to spot dots that stay lit (bright dots, or stuck-on pixels); on white or solid-color screens, dots that don’t light up (dark dots, or dead pixels); and on 50% gray, OLED burn-in (traces of the status bar or keyboard). The touch test divides the whole screen into a grid and paints each cell green as your finger passes over it, so unresponsive spots are left visible. Touch with several fingers and it also counts how many simultaneous touch points can be read (multi-touch). The refresh rate test measures the interval at which the browser redraws the screen for 3 seconds and tells you whether it is running at 60Hz, 90Hz, 120Hz or 144Hz. There’s also a checklist and copyable results for when you buy a used phone or monitor, want to check for initial defects, or want to test a device before selling it secondhand.
How to use Screen Checker | Test Dead Pixels, Burn-in, Touchscreen Response and Refresh Rate (Hz)
- 1Under “Dead pixels & burn-in”, press “Start full-screen test” (dimming the room a little makes problems easier to spot)
- 2Look closely all the way to the edges for dots that stay lit on the black screen and missing dots on the white, red, green and blue screens
- 3Tap (or click / press →) to move to the next color, check for burn-in on the gray screen, and for stripes or crushed tones on the gradient and level steps
- 4Under “Touch response”, trace your finger over the full-screen grid and make sure no cells are left without turning green. Touch with several fingers to see the simultaneous touch count too
- 5Under “Refresh rate”, press “Measure” and wait 3 seconds without touching the screen to see how many Hz it runs at
- 6Under “Screen info & checklist”, tick the items you’ve checked and record them with “Copy results”
Great for
- Check a used phone, iPad or monitor for dead pixels or burn-in right after buying it
- Check a new monitor or laptop for bright dots while it can still be exchanged for initial defects
- See whether an OLED phone shows burn-in from the status bar or keyboard
- Pin down exactly where part of the touchscreen seems not to respond
- Compare touch response at the edges and corners before and after applying a screen protector
- Find out how many points multi-touch supports (for example, 5 or more for gaming)
- Check whether a 120Hz or 144Hz screen or monitor is really running at its configured refresh rate
- Check the screen’s condition before selling it secondhand and summarize what to write in the listing
Good to know
- Dead pixels come in two kinds: “bright dots (stuck-on pixels)” that stay lit on a black screen, and “dark dots (dead pixels)” that don’t light up on a bright screen. Full-screen solid colors are the most reliable way to find either.
- Each pixel is made of red, green and blue subpixels. The human eye is most sensitive to green, so a green screen makes even small faults easy to see.
- If you find a dot, gently wipe the screen with a soft cloth and check whether it stays in the same place when the color changes. Dust and smudges look different depending on the color, while a dead pixel doesn’t move.
- Burn-in tends to occur on OLED screens that showed the same image for a long time, and its shape shows up faintly on gray around 50%. Turning up the screen brightness makes it easier to spot.
- A gradient that looks striped (banding) can be caused by 8-bit output or image processing settings, and is not necessarily a fault.
- The touch test fills in the cells in between even if you move your finger quickly. If the same spot never turns green no matter how slowly you trace it, the touchscreen may be faulty.
- Screen protectors, case edges, wet fingers and gloves all make touch response worse. Removing them and comparing helps you narrow down the cause.
- The refresh rate is calculated from the interval at which the browser redraws the page. Safari on iPhone has a setting that limits page rendering to 60Hz, and Android’s power saving mode or Smooth display setting can also drop it to 60Hz.
- When measuring the refresh rate, close other tabs and heavy apps and wait without touching the screen. Heavy processing increases “dropped frames”.
- Methods that claim to fix dead pixels by flashing the screen carry a risk of photosensitive seizures, so this tool doesn’t use them.
- Test results and the checklist are only saved in this browser and are never sent to a server.
Questions this tool answers
Use Screen Checker | Test Dead Pixels, Burn-in, Touchscreen Response and Refresh Rate (Hz) for searches like these:
- Check a phone or monitor for dead pixels in the browser
- Check for bright dots on a black screen
- Show an image for checking OLED burn-in
- Find spots where the touchscreen doesn’t respond
- Find out how many multi-touch points are supported
- Check whether a monitor or phone is running at 120Hz or 144Hz
- Learn how to check the screen when buying a used phone
- Check a monitor for initial defects
FAQ
- How do I check for dead pixels?
- Show solid black, white, red, green and blue full screen in turn and look for any dot of a different color. A dot that stays lit on the black screen is a “bright dot”, and a dot that stays black on a white or solid-color screen is a “dark dot (dead pixel)”. The trick is to dim the room a little, get close to the screen, and look all the way into the corners and edges.
- How do I check a phone for burn-in?
- Show gray at around 50% full screen and look at it with the brightness turned up. If the shapes of the status bar, navigation bar, keyboard or buttons of frequently used apps faintly remain, that’s burn-in. Checking with a dark gray too makes color non-uniformity and vertical lines easier to find.
- What’s the difference between a dead pixel and dust or dirt?
- A dead pixel stays in the same place even after you wipe the screen, and how it looks changes with the color shown (for example, it looks black only on the green screen). Dust moves or disappears when wiped, and smudges on the surface of the screen appear to shift position when viewed at an angle.
- How do I find spots where the touchscreen doesn’t respond?
- Open the touch test in full screen and trace your finger over the entire screen. Cells that respond turn green, so wherever cells remain un-green is where the response is weak. If the same spot never responds no matter how slowly you trace it, remove any film or case and try again, and if it’s still the same, ask about repair or replacement.
- How many multi-touch points are normal?
- Most recent phones and tablets support 5 or more simultaneous touches (many models support 10). In the touch test, add fingers one at a time and check the maximum number of simultaneous touches. The number a browser can read may be lower than the device’s spec because of OS or browser limits.
- How can I check whether 120Hz is working?
- Press “Measure” in the refresh rate test and wait 3 seconds without touching the screen. If it shows about 120Hz, browser rendering is also running at 120Hz. If it shows 60Hz, check low power mode or battery saver, Android’s “Smooth display”, your computer’s display settings (whether 144Hz or similar is selected), and the cable standard.
- Why does it show 60Hz even though my iPhone has ProMotion (120Hz)?
- Safari on iPhone has a setting that limits web page rendering to 60Hz to save power, so by default the page may not be able to measure 120Hz. It also drops to 60Hz when low power mode is on. Even if the screen itself supports 120Hz, the value measured in the browser can be 60Hz, so it isn’t necessarily a fault.
- What should I check on the screen when buying a used phone?
- Check for bright dots on a black screen, dark dots and color non-uniformity on a white screen, burn-in on a gray screen, unresponsive spots in the touch test, the number of simultaneous touches, and whether the refresh rate matches the spec. Going through this tool’s checklist and recording the results with “Copy results” makes it easier to explain the issue when returning the device or contacting the seller.
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