The viewport is the visible area of the page in the browser, measured in CSS pixels. It changes when resizing the window, opening sidebars, changing zoom or rotating the device.
Screen Resolution Checker
See viewport, resolution, DPR, estimated physical pixels and orientation
Not every browser pixel is a physical screen pixel
Browsers work with CSS pixels, a logical unit used for layout. HiDPI screens and page zoom change the relationship between CSS pixels and physical pixels, represented by devicePixelRatio. That is why the resolution reported by a web page can differ from the nominal resolution of a monitor or phone.
Read the current screen and test size changes
- Open the tool and immediately see current viewport, screen and DPR values.
- Resize the window, change zoom or rotate the device to observe values changing.
- Use refresh if the browser does not fire resize or orientation events automatically.
Sources and references for this tool
These references help contextualize formulas, standards, APIs and limitations used on this page. They do not replace professional validation when a result has legal, financial, medical or operational impact.
- Window.devicePixelRatioMDN Web Docs — Ratio between physical pixels and CSS pixels, including zoom and HiDPI displays.
- ScreenMDN Web Docs — Interface used for screen width, height, available area, color depth and orientation.
- CSSOM View ModuleW3C — Specification for viewport, screen and layout measurement APIs.