Screen checker
Turn CSS viewport, device pixel ratio, colour depth and diagonal into physical resolution, aspect ratio and PPI, and list full-screen solid-colour test swatches for dead pixels and backlight bleed.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Screen parameters
Physical resolution, aspect ratio, PPI and colour depth.
Enter the CSS viewport (e.g. 1920x1080) to inspect
CSS width: 0 · CSS height: 0 · Physical width: 0 · Physical height: 0 · PPI: 0
What this tool does
- Verify that the physical resolution reported by the system matches the CSS viewport times the pixel ratio reported by the browser.
- Work out PPI: enter the diagonal in inches and compare how dense a 27-inch 4K panel is against another screen.
- Check the colour depth the browser reports when gradients look banded on a supposedly high-depth display.
- Step through the solid-colour swatch list full screen to spot bright dots, dead pixels, colour casts and backlight bleed.
Example
Input
1920x1080
Output
CSS 视口：1920 × 1080 物理分辨率：3840 × 2160（设备像素比 2） 宽高比：16:9 对角线：27 英寸 → PPI 163.18 色深：24 位（真彩色，16 777 216 色） 每通道位数：8 位 可显示颜色数：16,777,216 标准色深档位：1 / 4 / 8 / 15 / 16 / 24 / 30 / 32 / 36 / 48 分辨率档位：4K UHD
Physical resolution = CSS viewport × device pixel ratio; PPI = √(w²+h²) ÷ diagonal inches.
Frequently asked questions
How is the physical resolution derived?
Straight from the definition of devicePixelRatio: physical pixels = CSS pixels × pixel ratio. A 1920×1080 CSS viewport on a 2× display is 3840×2160 physical pixels, which is what '4K' means here. The browser only exposes the CSS viewport and the ratio, so multiplication is the correct derivation.
Which PPI formula is used?
PPI = √(physical width² + physical height²) ÷ diagonal inches, from the Pythagorean theorem plus the definition of pixels per inch. Without a diagonal the PPI row is left blank, because any number would be invented.
What is the difference between 24-bit and 32-bit colour?
24-bit is 8 bits per RGB channel — 16,777,216 colours. The extra 8 bits in 32-bit are an alpha channel, so the colour count stays the same. What actually removes banding is a true 10-bit-per-channel (30-bit) or 36/48-bit mode.
How do I use the solid-colour test?
Tick the option and the result lists eight swatches: black, white, red, green, blue, mid grey, yellow and cyan with their hex values. Show each one full screen — black reveals bright dots, white reveals dark dots and stains, and the saturated colours reveal colour casts and edge bleed.
Can the reported values be changed?
Yes: browser zoom changes devicePixelRatio, so a zoomed page reports the zoomed equivalent. Reset zoom to 100% if you want the native values.
Keywords：屏幕检测screen check设备像素比device pixel ratioPPI坏点检测dead pixel test色深