Screen Tests — Dead Pixels, Refresh Rate & Colour
By Jayadeep · Last updated: August 2026 · How we test
Ten browser tests for finding panel defects and confirming your display is actually running at the specification you paid for.
A display can fail in two completely different ways, and they need completely different tests. The first is a physical defect: a subpixel that never lights, a pixel stuck at full red, a corner where the backlight leaks through a black frame. The second is a configuration failure, where the panel is flawless but the machine is driving it wrong — a 144Hz monitor running at 60Hz because Windows defaulted it there, or a screen rendering at a non-native resolution so everything looks faintly soft. This page covers both, and it is worth knowing which one you are chasing before you start.
Physical defects are found by elimination, using solid colour fields. The reason full-screen solid colours work so well is that ordinary content hides faults: a dead pixel is invisible in a busy photograph and obvious against plain white. Each colour reveals a different class of defect. White shows dead and dark subpixels along with dust on the glass. Black exposes stuck-bright pixels, backlight bleed along the panel edges, and the IPS glow that shows up in dark corners. Pure red, green and blue each drive one subpixel channel at a time, which is how you tell a fully dead pixel from a partially stuck one — a pixel that appears on red but vanishes on green has a failed green subpixel specifically.
Configuration problems need measurement instead. The refresh rate test counts real frames delivered to the browser over a sampling window and reports the rate the panel is actually achieving, which is frequently not the number printed on the box. This catches the single most common new-monitor disappointment: a high-refresh display plugged in and left at the operating system's conservative default. The FPS test does the related job of showing how many frames your machine is producing, and the two together explain most "it does not feel smooth" complaints.
One warning about pixel defects and warranties. Manufacturers publish dead-pixel policies that specify how many faulty pixels a panel must have before it qualifies for replacement, and the thresholds differ by brand, panel class and whether the defect is bright or dark — a single stuck-bright pixel often qualifies where several dark ones do not. If you have just bought a monitor, test it now rather than later. Return windows are short and almost always shorter than the warranty.
Every screen test
Which test do I need?
Decide whether you are hunting a physical panel defect or a configuration problem, then pick the matching row. The two need completely different tests and confusing them wastes a lot of time.
| What you are seeing | Start here | Why this one |
|---|
| I just bought a monitor and want to check it | Dead Pixel / Screen | Run the full colour cycle first. It steps through white, black and the three primaries, which together expose every common panel defect in about a minute. |
| I think I have a dead pixel | White Screen | A solid white field makes dark defects obvious. Then check the same spot on black — a dot visible on both is dead, a dot visible on only one is stuck. |
| My screen looks blotchy in dark scenes | Black Screen | Full black in a dark room is the only reliable way to judge backlight bleed and IPS glow. Both are normal in small amounts; heavy clouding near one edge is not. |
| My monitor does not feel as smooth as advertised | Refresh Rate Test | This measures the refresh rate you are actually getting. If a 144Hz panel reports 60, the panel is fine and the display setting is wrong. |
| Games feel choppy but the monitor is fine | FPS Test | Refresh rate is what your screen can show; FPS is what your machine produces. This test measures the second one. |
| I need my exact resolution or GPU for a support ticket | Screen Resolution & Info | Reports resolution, window size, pixel ratio, GPU, OS and memory as the browser sees them — copy it straight into the ticket. |
| I want to check my colour vision, not the screen | Color Blindness Test | An Ishihara-style screening for red-green colour vision deficiency. It screens; it does not diagnose. |
Troubleshooting guides
Deeper reading on panel defects, refresh rate behaviour and what manufacturers will and will not accept as grounds for a replacement.
- Check a monitor for dead pixels — Test a new monitor before the return window closes.
- Dead pixel vs stuck pixel — Tell them apart and fix what you can.
- Testing a new monitor — A quick checklist before the return window ends.
- Refresh rate explained — What Hz means and whether higher is worth it.
- Refresh rate vs frame rate — How Hz and FPS work together.
- Monitor stuck at 60Hz — Unlock 120Hz or 144Hz on your display.
- How to test your FPS — Check display and in-game frame rates.
- Find your screen resolution — See your resolution and aspect ratio instantly.
- How to test for colour blindness — Check your colour vision with plate tests.
- Types of colour blindness — Red-green, blue-yellow and total, explained.
- How to Test a Monitor for Ghosting — A practical walkthrough for finding ghosting, overshoot and motion blur on any monitor, and what to change in your display's settings when you find it.
- How to Try to Fix a Stuck Pixel — What actually works on a stuck pixel, what does not, and how to tell a stuck pixel from a dead one before you waste time on a fix that cannot help.
- How to Check an OLED Screen for Burn-In — How to find burn-in on an OLED phone, monitor or TV, how to tell it apart from temporary image retention, and what actually reduces the risk.
- How to Check Your Screen for Colour Banding — How to spot colour banding on a monitor, why it often comes from a cable or a setting rather than the panel, and what to change to fix it.
- IPS vs OLED — Dead Pixels and Burn-In — IPS and OLED panels fail in completely different ways.
- 60Hz vs 120Hz vs 144Hz — What You Actually Notice — What changes between 60Hz, 120Hz and 144Hz, where the returns diminish, and why your frame rate and display settings matter more than the number on the box.
Frequently Asked Questions
What is the difference between a dead pixel and a stuck pixel?
A dead pixel receives no power and stays black on every background. A stuck pixel is still powered but frozen on one colour, so it shows as a bright red, green, blue or white dot. The practical test is to view the same spot on white and on black: a dot visible on both is dead, a dot visible on only one is stuck. Stuck pixels sometimes recover; dead ones effectively never do.
How many dead pixels before a manufacturer replaces my monitor?
It depends entirely on the brand and the panel class, and there is no single industry number. Policies distinguish bright defects from dark ones and usually allow more of the latter. Check your specific manufacturer's published pixel policy before starting a claim, and test within the retailer's return window, which is normally far shorter and far easier to use than a warranty claim.
Is backlight bleed a defect or is it normal?
Some is normal on any edge-lit LCD, particularly in the corners, and it is not usually covered as a fault. It becomes a defect when it is severe enough to be visible in ordinary content rather than only on a full black field in a dark room. OLED panels do not have a backlight at all, so they do not exhibit bleed — though they have their own failure modes.
Why does the refresh rate test report less than my monitor's rating?
Most often the operating system is driving the panel at a lower rate than it supports, which is a common default after a fresh install or a cable change. It can also be a cable or port limitation — bandwidth caps the combination of resolution and refresh rate you can run. Check your display settings first, then the cable specification.
Can a browser test really measure my refresh rate accurately?
It measures how frequently the browser is able to present frames, which tracks the panel's actual refresh rate closely on a machine that is not heavily loaded. Close other demanding tabs and applications for the cleanest reading. It is a reliable indicator, not laboratory instrumentation.
Will the solid colour screens damage an OLED display?
Brief use for testing is fine. Prolonged display of a static bright field on an OLED is not advisable, because OLED subpixels age with use and a static image held for a long time can leave persistent retention. Run the test, note the result, and move on rather than leaving a solid field on screen for hours.
Other test categories
Audio tests · Controller tests · Input tests · Performance tests · Camera tests
These tests only fill your screen with colour fields and count frames the browser presents — no data about your display is collected or sent anywhere. How we validate these tests.