Dead Pixel & Refresh Rate Test
Find dead or stuck pixels with full-screen black, white, red, green, blue and gray, check gradient banding, estimate refresh rate and watch a ghosting bar.
Privacy: this tool only produces picture or sound and sends nothing about your test anywhere. Ads on this page (Google AdSense) work separately — see the privacy policy.
To log Wi-Fi or internet drops and Bluetooth connects and disconnects over time, use the Windows program PortDock Hardware Tester (free).
Order: Black → White → Red → Green → Blue → Gray 25% → Gray 50% → Gray 75% → Gray gradient → RGB gradients
Counted from how often the browser draws. With several monitors it may show the primary monitor's rate, and variable refresh (G-SYNC, FreeSync, VRR), power saving or battery mode can make it differ. Keep this tab in front and wait a few seconds.
Gradient (banding)
The top bar is a smooth gradient and the bottom bar has 32 steps. If the top shows clear step-like bands, look at color depth, color calibration or picture settings.
Moving bar (ghosting)
A long blurry tail behind the bar points at response time (ghosting); a bar that jumps points at skipped frames. Compare the monitor's overdrive settings at the same speed.
How to use
- Wipe the screen and press «Full-screen colors». Scan the whole screen slowly on each color.
- A lone bright dot on black may be a stuck pixel; a lone dark dot on white may be a dead pixel. A dot visible only on red, green or blue may be one faulty subpixel.
- On the gray steps look for clouding (uneven brightness) and backlight bleed (bright edges). Bleed is easiest to see on black in a dark room.
- If you are unsure whether a dot is dust, switch colors and see if it stays put. Dust looks like the same shadow on every color.
On equipment PCs too
Use it when receiving or replacing HMI, panel PC or inspection monitors to check pixels and uniformity before installation. For how many defects are acceptable, see the manufacturer's warranty terms. For cameras and input devices, see the webcam test and the mouse double click test.
FAQ
How many dead pixels qualify for a replacement?
It varies by maker and product (some promise zero defects, others set counts and positions). Photograph what you find here and check the warranty terms.
The refresh rate differs from my monitor setting
First check Settings → Display → Advanced display in Windows. This is a browser estimate, so several monitors, variable refresh or power saving can change it. Keep the tab in front without moving the mouse for a few seconds and it settles.
Full screen does not work
Browsers without the Fullscreen API (such as Safari on iPhone) get a page-covering layer instead. If the address bar shows, rotate to landscape or scroll to hide it.