How to test your monitor
- Wipe the screen with a dry microfiber cloth first, so dust isn’t mistaken for a bad pixel.
- Press Dead pixel test. The screen fills with black, then white, red, green, blue, cyan, magenta and yellow. Click, tap or press → to move to the next color, ← to go back, or Esc to stop.
- On each color, look slowly across the whole screen from about 30 cm (one foot) away. A magnifying glass or your phone’s camera zoom helps on high-resolution screens.
- Run Gradient & banding to check that color ramps are smooth.
- Dim the lights and run Uniformity & bleed to look for glowing edges and uneven patches.
- Check the Refresh rate box matches what you paid for, such as 144 Hz or 165 Hz.
What you might see
- Black dot on white or colors: a dead pixel. It gets no power and is usually permanent.
- Colored dot on black: a stuck pixel, where one or more of its red, green and blue subpixels stays on. These can sometimes be fixed.
- A dot that is wrong on only some colors: a single stuck or dead subpixel. A red-only dot that disappears on the red screen is a stuck red subpixel.
- Stripes in gradients: color banding. Mild banding is normal on 6-bit and many 8-bit panels and in compressed video; strong banding can also come from color profiles, night light modes or low color depth settings.
- Glowing edges or corners on dark gray: backlight bleed, common on LCD (IPS and VA) panels. A faint, even silver glow on IPS panels seen at an angle is IPS glow, which is a property of the panel, not a fault.
- Blotchy or uneven gray: poor uniformity or the “dirty screen effect”, more noticeable on large TVs.
What to do about bad pixels
- Make sure it’s really a pixel. Dust on the screen moves when you wipe it, while a pixel fault stays put on every color except the one that matches.
- Try the stuck pixel fixer. Drag the flashing box over the pixel and leave it running for 10–20 minutes, then check again. Rapid color changes can unstick a subpixel that is stuck on or off. It doesn’t help dead pixels.
- Gentle pressure (at your own risk). Some people revive a stuck pixel by turning the screen off and pressing very lightly on the spot with a soft cloth over a fingertip. Pressing too hard can make things worse, so this is a last resort.
- Use the warranty or return policy. If the monitor is new, return or exchange it within the shop’s return window. Otherwise check the manufacturer’s pixel policy; many publish how many bright, dark and subpixel faults qualify for a replacement.
About refresh rate
Refresh rate is how many times per second the screen draws a new picture, measured in hertz (Hz). Most office monitors and laptops run at 60 Hz, while gaming monitors often run at 144 Hz, 165 Hz, 240 Hz or higher. A higher refresh rate makes motion, scrolling and the mouse pointer look smoother.
This page reads the rate by timing how often the browser draws frames and taking the median of the last few seconds. If it shows a lower number than your monitor supports, the display is most likely set to a lower rate, the cable or port can’t carry the full rate, or your browser is limiting animations to save power. With several monitors, browsers usually follow the refresh rate of the screen the window is on, so drag the window to the monitor you want to test and wait a few seconds.
Resolution and scaling
Resolution (pixels) is the number of physical pixels the browser reports for your screen, such as 1920 × 1080 (Full HD), 2560 × 1440 (QHD) or 3840 × 2160 (4K). Scaled size is the size your system uses for laying out windows and text, and the multiplier is your display scaling. A 4K monitor set to 150% scaling, for example, shows 2560 × 1440 at 1.5×. Browser zoom also changes the multiplier, so set zoom to 100% for a true reading. Color gamut and HDR show what your browser says the current display supports; HDR shows Yes only when HDR is turned on in your system settings.
Is this test private?
Yes. The test patterns are drawn by your browser, and the screen information is read on your device. Nothing is uploaded or stored.
Frequently asked questions
What is the difference between a dead pixel and a stuck pixel?
A dead pixel stays black on every color because it gets no power, so it shows up clearly on the white screen. A stuck pixel is lit in one color, often red, green or blue, and shows up on the black screen and on colors it doesn’t match. Stuck pixels can sometimes be revived; dead pixels usually can’t.
Why does the refresh rate show 60 Hz on my 144 Hz monitor?
The monitor is probably running at 60 Hz. On Windows, open Settings › System › Display › Advanced display and choose the higher refresh rate. On a Mac, open System Settings › Displays and pick it from the Refresh rate menu. Also check the cable: older HDMI cables and ports often can’t carry high refresh rates at full resolution, while DisplayPort usually can.
How accurate is the refresh rate reading?
The page measures how often your browser draws a new frame, which follows the display’s refresh rate. It is accurate when the tab is visible and the computer isn’t busy. Battery-saving modes, a hidden tab or variable refresh (G-Sync, FreeSync, ProMotion) can make the reading lower or change it from moment to moment.
How many dead pixels are acceptable?
It depends on the manufacturer. Many brands follow the ISO 9241-307 pixel fault classes and will only replace a monitor after a certain number of faulty pixels, while others promise zero bright pixels. Check the warranty or the pixel policy on the manufacturer’s website, and test a new monitor right away so you can return it within the shop’s return window.
Can I test a phone or TV screen with this?
Yes. Open the page on the phone or in the TV’s browser and tap the screen to move through the colors. On phones that don’t support fullscreen pages, the colors still fill the browser window; scroll the address bar away for the best view.
Is the stuck pixel fixer safe?
It only changes the colors of pixels in a small box, which can’t harm a screen. It does flash rapidly, so don’t use it if you are sensitive to flashing lights, and don’t look at it while it runs. Results vary: it helps some stuck pixels and does nothing for dead ones.