Test your screen's device pixel ratio (DPR). Detect Retina, HiDPI, and standard displays in one click.
Device Pixel Ratio (DPR) is the ratio of physical pixels to CSS (logical) pixels on your screen. A DPR of 2 means there are 4 physical pixels (2×2) for every CSS pixel, resulting in a sharper display — known as Retina on Apple devices.
Standard monitors have a DPR of 1. Most modern smartphones have DPR of 2-4. This matters for web developers who need to serve higher-resolution images for HiDPI displays.
On DPR 2 screens, a 200x200 CSS image renders at 400x400 physical pixels. Standard resolution images appear blurry on Retina displays. Web developers use srcset to serve 2x images for DPR 2 and 3x for DPR 3 screens, and the CSS media query for min-device-pixel-ratio targets Retina displays.
Standard desktop monitors: DPR 1.0-1.5. MacBook Pro Retina: DPR 2.0. iPhone 14 and later: DPR 3.0. Most Android flagships: DPR 2.5-4.0. Budget Android phones: DPR 1.5-2.0. Higher DPR means sharper images at the same physical size.