What this test can tell you
The checker reports CSS screen dimensions, browser viewport size, available screen area and device pixel ratio. Resize the window to compare viewport changes.
Logical CSS dimensions are not guaranteed native panel pixels. Scaling, desktop page zoom, orientation and privacy protections can affect these browser-provided values.
How to use it
- Read the reported screen size and compare it with your operating system’s display settings.
- Resize the browser window to see the viewport dimensions change.
- Reset desktop page zoom to 100% when comparing pixel-ratio readings.
- Move the window to another display and check again.
Screen resolution, viewport and pixel ratio are different
Screen dimensions describe the display area reported to the browser in CSS pixels. The viewport describes the current page area. Device pixel ratio describes the scale between CSS pixels and device pixels; desktop page zoom can change it. None of these readings alone proves the native resolution of the panel.
| What you see | What it means / next check |
|---|---|
| Screen size stays the same when the window shrinks | Expected: the browser window changed, while the reported display size did not. |
| Viewport is smaller than the screen | Browser controls, window size and operating-system UI reduce the area available to the page. |
| Pixel ratio changes with desktop page zoom | Expected in many desktop browsers. Do not use CSS dimensions multiplied by the current pixel ratio as a guaranteed native-panel measurement. |
Methods and sources
These explanations describe this page’s browser test and its limitations. Last updated . Reference documentation:
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Why does a 4K display report a smaller screen size?
Operating-system display scaling can make a high-resolution panel report fewer CSS pixels. Check the native resolution and scaling setting in your operating system instead of treating the browser’s CSS dimensions as physical pixels.
Why do browser readings differ between devices?
Browsers expose logical display metrics. Scaling, zoom, orientation and privacy protections affect the values. The page reports what the browser exposes rather than guessing a hardware model.
Frequently asked questions
Can a website detect my exact native monitor resolution?
Not reliably in every setup. This checker reports CSS screen dimensions, viewport dimensions and device pixel ratio. Native panel resolution should be confirmed in operating-system display settings or the manufacturer’s specifications.
Is viewport size the same as screen resolution?
No. The viewport is the area available to the current page. It can be smaller than the display because of window size, browser controls and other interface elements.
Does this check need permission or upload device data?
No permission is requested. The readings are displayed locally and are not sent by this tool to a server.