Dead & stuck pixels
Nine pure colors, edge to edge. A dead pixel stays black, a stuck one stays lit.
1 minGuide
Monitor Gamma & Black Level Test
Black level, white saturation and a gamma target, drawn on real pixels. 100% in your browser - nothing is uploaded.
1 min3 patterns
Click the preview to run it full screen
Your display
Updates when you move the window to another screen- Resolution
- ---
- device px
- Pixel ratio
- ---
- devicePixelRatio
- Refresh rate
- ---
- measured in this browser
- Color gamut
- ---
- reported by the browser
- HDR
- ---
- standard range
- Orientation
- ---
- current
How to run the monitor gamma & black level test
01Reset the picture mode
Standard or sRGB, with dynamic contrast, black stabiliser and eco modes off.
02Black level
Find the lowest numbered square you can still see against black.
03White level
Find the highest numbered square that still stands apart from white.
04Blur the gamma target
Step back a couple of metres or squint until the stripes turn to flat grey.
05Read your gamma
The patch whose solid center disappears into its stripes is your gamma.
What to look for
- Black level: the first squares (1 to 3) should be faintly visible. If nothing shows below 10, shadows are crushed.
- White level: squares up to about 250 should still stand apart. If everything above 240 merges, highlights clip.
- Gamma: the center that blends in. Up close the stripes must look like sharp lines, not flat grey.
- The same results on the edges as in the middle of the screen.
What counts as a defect
- Squares below 16 merging into black and above 235 merging into white together point to limited range RGB, not the panel.
- Gamma well above 2.2 makes images look dark and heavy; well below it, flat and washed out.
- Faint first squares are normal on many LCDs in a bright room. Judge black level in dim light.
- If the stripes look grey even up close, the image is being scaled and the gamma reading is not valid.
What to do next
- Set the graphics driver output to full range RGB and the monitor’s HDMI black level to match, then test again.
- Use the monitor’s gamma setting if it has one: pick the step that makes the 2.2 patch blend in.
- Lower contrast one step at a time until the brightest white squares separate again.
- For an exact curve across all tones, use a hardware colorimeter; this target checks the mid-tone point by eye.
Other screen tests
Each one checks a different part of the panel. The guided check runs them all in order.
Uniformity & clouding
Flat greys and white show clouding, dirty-screen effect and tinted zones.
1 minGuide
Banding & gradients
256 equal steps per ramp. A good panel shows them evenly, a weak one clumps them.
1 minGuide
Sharpness & geometry
One-pixel grids, checkerboards and circles expose scaling blur and bad geometry.
1 minGuide
Refresh rate & tearing
Measures the real frame rate in this browser and shows tearing on a moving bar.
30 sGuide
About the monitor gamma & black level test
Three checks tell you whether the monitor shows the full range of tones. Black level: can you tell the darkest greys from black, or are shadows crushed? White saturation: do the brightest greys stay apart, or do highlights clip? Gamma: is the mid-tone curve at the 2.2 that web pages, games and photos are made for? The gamma target uses 1 px stripes on your screen’s own pixel grid, so it works at any scaling setting.
It is one of the tests in the Screen & Monitor Test, which also runs a guided check through every test and ends in an inspection reportfor a return or RMA. Every pattern is drawn on your screen's own pixel grid, 100% in your browser - no upload, no install, no account needed.
Frequently Asked Questions
2.2 for everyday use: web pages, Windows, games and most photos are made for it, and it is close to the sRGB curve. 2.4 is the reference for video mastered for a dark room. Higher values look darker and richer, lower values look brighter and flatter.
Usually a setting: limited range RGB sent over HDMI, a black level or shadow setting on the monitor, or a bright room washing out the darkest greys. Some panels also crush near-black tones on their own. Fix the range first, then judge in dim light.
Good enough to tell 2.0 from 2.2 from 2.4 by eye, and to see whether a setting moves you towards the target. It checks the curve at one point, where 50% light should be. A colorimeter measures the whole curve and every color.
Safari on iPhone does not allow web pages to go truly full screen. The test fills the whole visible area and hides all controls instead; rotate to landscape, or add the page to your Home Screen, to get the most of the panel in view. iPad and Android support real full screen.
No. Every pattern is drawn locally in your browser, and the inspection report is built and downloaded on your device. Nothing about your screen or your results leaves the browser, and no account is needed.
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