Screen Size Checker

What is Screen Size Checker?

Screen Size Checker is a free browser tool that shows the dimensions your device actually reports: screen resolution, CSS viewport size, device pixel ratio, and related density details. It is built for designers, developers, support teams, and anyone comparing monitors or troubleshooting responsive layouts. Beyond the live readout, the site includes calculators and references for PPI, aspect ratio, common resolutions, and responsive testing helpers. Everything runs client-side after you open the page, so you get an immediate snapshot of the current browser window without installing an extension.

How to use Screen Size Checker?

1. Open screensizechecker.com in the browser you want to measure.
2. Read the live screen resolution, viewport (CSS px), and device pixel ratio.
3. Resize the window or rotate the device and watch the values update.
4. Use linked tools such as PPI calculator, aspect ratio, or responsive tester when needed.
5. Compare against the common-resolution chart if you are picking a monitor or debugging a layout.

Core Features

• Instant resolution readout — Screen size and viewport update in the current browser.
• Device pixel ratio — See DPR and density context for sharp UI and image decisions.
• No install — Works online without signup, extension, or app download.
• PPI and aspect tools — Calculators for pixel density, aspect ratio, and related checks.
• Responsive helpers — Compare screens and run quick responsive tests from the same site.
• Resolution reference — Charts for common Full HD, QHD, 4K, and laptop sizes.

Use Cases

• Responsive QA — Confirm viewport and DPR before filing a layout bug.
• Monitor shopping — Compare advertised sizes against real CSS and physical density.
• Design handoff — Capture exact browser dimensions when reviewing a mock on device.
• Support triage — Ask users to open the page and report their detected resolution.
• Teaching CSS pixels — Show the difference between screen pixels and CSS viewport.