What’s wrong with my screen? Find the right test
| What you see | Likely cause | Test |
|---|---|---|
| A tiny black or colored dot that never changes | Dead or stuck pixel | Dead pixel test |
| Light glowing from the edges or corners on dark scenes | Backlight bleed or IPS glow | Backlight bleed test |
| Patches, clouds or darker corners on gray | Poor uniformity / dirty screen effect | Gray uniformity test |
| A faint leftover image of a logo, taskbar or keyboard | Burn-in or image retention | Burn-in test |
| Moving objects leave a trail or smear | Ghosting / slow response time | Ghosting test |
| A 144 Hz+ monitor doesn’t feel smooth | Wrong refresh rate | Refresh rate test |
| Stripes in skies and gradients | Color banding | Color banding test |
| Shadows look crushed or washed out | Brightness / black level | Brightness test |
| Colors look too cold, warm or tinted | Calibration | Monitor calibration |
| Text looks blurry or has colored fringes | Scaling, sharpness or subpixel layout | Text clarity test |
| The screen flickers or causes eye strain | PWM or VRR flicker | Flicker test |
| Parts of the touchscreen don’t respond | Touch dead zones | Touch screen test |
How to test a new monitor
Most stores give you a short window to return a display for any reason, and a defect is far easier to sort out in that window than through a warranty claim. Run these checks on day one, in this order:
- Let it warm up and set it up. Give the screen 15–30 minutes to reach a stable temperature, use the native resolution and set the refresh rate in your OS. Confirm it with the refresh rate test — a 144 Hz monitor running at 60 Hz is the single most common setup mistake.
- Check for dead and stuck pixels. Run the dead pixel test in fullscreen, on every color, edge to edge. Stuck pixels can sometimes be revived with the stuck pixel fixer.
- Check the dark end. In a dark room, use the backlight bleed test on an LCD or the OLED test on an OLED. Some glow is normal; bright patches at the edges are not.
- Check uniformity. The gray uniformity test shows clouding, vignetting and the dirty screen effect that are invisible on busy content but obvious in games and video.
- Check motion. The ghosting test shows trailing and overshoot; use it to choose the right overdrive setting.
- Dial it in. Use the monitor calibration guide to set brightness, contrast, gamma and color temperature, and the text clarity test to make text sharp.
Tips for accurate results
- Clean the screen first with a dry microfiber cloth — dust is the most common false alarm.
- Use fullscreen so the pattern reaches every edge.
- Turn off night mode and adaptive features (Night Light, Night Shift, True Tone, eye-care modes, dynamic contrast) while testing; they change what you see.
- Mind the room. Test dark-scene problems in a dark room and color problems in normal light. Bright reflections hide defects.
- Use the native resolution and 100% browser zoom for pixel-level tests like sharpness and gamma.
Frequently asked questions
How do I test my screen?
Run the quick check at the top of this page in fullscreen: it steps through white, black, red, green, blue, gray, a gradient and a motion test, with a hint for what to look for on each. If something looks off, open the dedicated test for that problem from the list below for a closer look and an explanation of what you are seeing.
What should I test on a new monitor?
Within the return window, check for dead pixels, backlight bleed (LCD) or near-black issues (OLED), uniformity, that the refresh rate matches what you paid for, and ghosting at your chosen overdrive setting. Then set it up with the calibration guide.
Are online screen tests accurate?
For finding defects — dead pixels, bleed, uniformity problems, banding, burn-in, ghosting — yes: they show the same full-screen patterns that dedicated software uses, and your eyes do the judging. They cannot measure things that need an instrument, like brightness in nits or color error (ΔE). Where a measurement is possible in the browser, such as refresh rate, our tests measure it precisely.
Why should I use fullscreen?
In a normal window the edges of the panel aren’t covered and the surrounding page distracts your eye. Fullscreen fills every pixel with the test pattern. Press F or click the test area. On iPhone, Safari doesn’t support true fullscreen, so the test fills the browser window — add the page to your home screen for an edge-to-edge view.
Do these tests work on phones, tablets and TVs?
Yes. Every test runs in a modern browser on Windows, macOS, Linux, ChromeOS, Android and iOS, and most work in smart-TV browsers with the remote’s arrow keys. There are dedicated guided checks for phones and TVs, and a touch screen test.
Is anything uploaded or installed?
No. Every test runs entirely in your browser. Nothing is installed, nothing is uploaded and no account is needed.