There is a classic stage in web development where a layout looks fine on one computer and mysterious everywhere else. The Screen Size page gives that conversation some numbers.
The page shows the current viewport dimensions alongside the browser’s inner and outer window sizes, screen dimensions, device pixel ratio, and orientation. As the window changes, the readout updates.
Those measurements describe related but different things. The viewport is the area available to the page; the physical screen and the browser’s outer window are not necessarily the same size. Browser controls, resizing, zoom, and device scaling can all affect what someone is actually looking at.
For a support or layout discussion, the useful result is a compact page someone can open and report back from. Instead of only saying that a button is off-screen, there is a specific browser view to compare with the layout’s assumptions.
The page does not fix responsive CSS on its own. It makes a few otherwise hidden conditions visible, which helps narrow the next question. A screenshot and the relevant dimensions can be much more informative together than either one alone.
Small tools like this reduce guesswork around other projects. A one-purpose diagnostic page does not need accounts, saved dashboards, or an elaborate setup to be worth using.
Sometimes the fastest path to fixing an interface is first finding out how much room the interface really has.
Update history
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- — Converted automated article narration to neutral third person and added public update history. No application functionality changed. GitHub source