Zoom & DPI Detector
The zoom estimate compares window frame width to page width; a desktop heuristic that docked dev tools or side panels can throw off. On phones, pinch zoom doesn’t change it; watch the PINCH ZOOM plate instead. Everything is read locally and nothing leaves your device.
How it works
仕組みThis detector estimates your current browser zoom level, reports your device pixel ratio, and derives the effective CSS DPI (96 × pixel ratio), three numbers that quietly reshape every page you visit. The zoom estimate compares the window’s outer frame width to the page width, a desktop heuristic that updates live as you press Ctrl/Cmd with + or −; on phones, the separate pinch-zoom meter reads the visual viewport scale instead. It is genuinely a your-own-browser question: zoom and scaling are personal settings that no external page or chart can see for you.
On a normal desktop window it is usually within a few percent. But it leans on outerWidth versus innerWidth, so anything occupying the window frame (docked dev tools, a bookmarks sidebar, some extensions) skews it. If the number looks wrong, close side panels and read it again after a small zoom nudge.
Device pixel ratio is how many physical pixels the display packs into one CSS pixel: a Retina laptop reports 2, a 150%-scaled Windows monitor 1.5. Browser zoom multiplies on top, and in most browsers it actually raises the reported pixel ratio too, which is why the CSS DPI meter moves when you zoom.
Pinch zoom magnifies the rendered page without changing its layout width, so the outer/inner comparison never moves. Mobile browsers expose it separately through the visual viewport API, which is what the PINCH ZOOM plate shows; it reads 1× until you actually pinch, where supported.