A used monitor can be a good deal, but a normal desktop wallpaper hides many problems. Before paying, test solid colors, black level, grey uniformity, ports, refresh rate, and signs of repair. Bring the right cable and allow enough time to inspect it properly.
Use the ScreenTest.run tools for quick full-screen checks on the seller's computer or your own laptop.
Start with Pixels and Surface Condition
Run white, black, red, green, and blue screens. Look for dead pixels, bright stuck pixels, scratches, coating marks, and dust trapped under the surface. Clean only gently; do not press hard on a panel you do not own yet.
| Check | Best screen | What to look for |
|---|---|---|
| Dead pixels | White | Tiny black dots |
| Stuck pixels | Black and RGB colors | Bright colored points |
| Burn-in or image retention | Grey / cyan / magenta | Faint UI shapes or logo shadows |
| Surface damage | Screen off and white screen | Scratches, coating wear, pressure marks |
Check Backlight, Black Level, and Uniformity
Open a black screen in a dim room if possible. Fixed bright patches can indicate bleed or pressure. Then use a grey screen to find dirty screen effect, yellowing, clouding, or uneven brightness.
Older LCDs may lose brightness or develop warmer corners over time. The key question is whether the unevenness is visible in the work or games you actually use.
Inspect Ports, Stand, and Repair Signs
Check every port you plan to use. Wiggle the cable gently and watch for flicker. Inspect screws, bezel seams, stand mount, and back cover gaps. Uneven seams, missing screws, or pry marks do not always mean disaster, but they are reasons to negotiate or walk away.
If the monitor OSD shows power-on hours, record it. Treat the number as one clue, not perfect proof, because some displays do not show it and some service menus can be reset.
Confirm Refresh Rate Before Paying
If the monitor is advertised as 144Hz or higher, set that mode in the operating system and verify it with the Refresh Rate Test. Also run a moving frame test to look for skipped frames or flicker.
Bring the cable you intend to use. A seller's old cable can make a good monitor look limited, and a direct cable test is cleaner than guessing.
Conclusion
A used monitor test should be practical and unemotional: pixels, surface, burn-in, black level, uniformity, ports, and refresh rate. If the seller refuses a short test, that is useful information by itself.
FAQ
What is the first thing to test on a used monitor?
Start with solid color screens for pixels and surface defects, then check black and grey screens for bleed and uniformity.
How can I find burn-in?
Use grey, cyan, magenta, and other flat colors. Look for faint taskbars, logos, windows, or repeated UI shapes.
Should I buy a monitor with one dead pixel?
Only if the price reflects it and the pixel location does not bother you. For design or close-up work, even one central defect can be annoying.
Related Tests and Guides
Run a Quick Used Monitor Check
Use solid screens and refresh-rate tests before you hand over the money.
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