Check your screen resolution, viewport size, pixel ratio, and DPI online. Free, instant, updates live as you resize.
This tool shows your screen's resolution, the browser viewport's current visible size, device pixel ratio (used for high-DPI/Retina-style displays), available screen space, color depth, and orientation. The viewport size updates live as you resize your browser window, making this useful for checking exactly what size your browser window currently is — handy for responsive web design testing or troubleshooting display scaling issues.
It's the ratio between physical screen pixels and CSS pixels. A ratio of 2x (common on Retina-style displays) means each CSS pixel is rendered using a 2×2 grid of physical pixels, resulting in sharper text and images.
Screen resolution is your entire display's pixel dimensions. Viewport size is just the visible area of your browser window, which is usually smaller — especially if your browser isn't maximized or has toolbars/panels open.