Debug viewport quickly
What Is My Viewport Size? Live Browser Viewport Checker
Live innerWidth, innerHeight, visualViewport, and safe-area values in CSS pixels for responsive debugging, mobile layout testing, and CSS viewport unit checks.
Viewport size vs screen resolution
Your screen has a fixed hardware resolution; your viewport is what CSS layouts use, the visible area of the page that changes with window size, zoom, and mobile browser chrome.
Screen resolution
Hardware pixels from your device panel.
Viewport size
CSS layout area after browser UI and zoom.
Need hardware details? Check screen size checker or CSS viewport units (vh & dvh).
When you need this tool
Bug reports
Capture exact repro sizes like 390×844, DPR 3.
Layout checks
Validate breakpoints and 100vh behavior on mobile.
Safe area debugging
Read env() insets for notched and dynamic-island devices.
Viewport unit testing
Pair with dvh comparison to compare vh, svh, lvh, and dvh.
Tip: rotate your device to instantly verify portrait and landscape behavior.