Why does my screen show 1920x1080 when I have a 4K monitor?

Windows and macOS scale the logical resolution for readability. The browser sees the scaled resolution, not the physical pixel count. Multiply by devicePixelRatio to get the native size.

What is devicePixelRatio?

It is the ratio of physical pixels to CSS pixels. A value of 2 means one CSS pixel is rendered as a 2×2 block of physical pixels, common on retina displays.

Does the tool work on phones?

Yes. It reports the viewport, screen, and devicePixelRatio exactly as the mobile browser sees them.

Screen Resolution Checker

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