Network · Browser
What is my viewport size?
The width and height your browser gives this page, in CSS pixels. Drag the window edge or rotate your phone and the numbers update live.
Your viewport size
Details
How to read your result
The large number is window.innerWidth by window.innerHeight. In the CSSOM View Module this is the viewport including any rendered scrollbar. That is also the width that CSS media queries compare against: Media Queries Level 5 defines the width feature as the viewport width including the size of a rendered scroll bar.
The layout viewport row uses document.documentElement.clientWidth, which leaves the scrollbar out. The gap between the two is shown as the scrollbar width. The visual viewport row (from window.visualViewport) is what you are actually looking at, so it shrinks when you pinch-zoom on a phone or when the on-screen keyboard opens.
To test a responsive layout, resize the window and read the width when the layout changes. That is the breakpoint to put in your media query.
Sources (retrieved October 2026): CSSOM View Module (W3C); Media Queries Level 5 (W3C).
Frequently asked questions
What is a viewport?
It is the area of the browser window in which the page is shown. Media queries and responsive layouts work from its size, not from the size of your screen.
Why is innerWidth bigger than the layout viewport?
innerWidth includes the scrollbar, while the layout viewport (documentElement.clientWidth) does not. On systems with overlay scrollbars the two are equal.
Does the viewport include the browser toolbar?
No. The viewport is only the page area. The outer window row shows the whole browser window including toolbars and borders.
Why does it change when I zoom?
Browser zoom changes the size of a CSS pixel, so the same window holds fewer CSS pixels when you zoom in. That is why zooming in can trigger a mobile layout on a desktop.
Is anything sent to a server?
No. The size is read in your browser and nothing is stored or sent.
Private by design
This tool reads values from your own browser and shows them on this page. The tool does not store them, send them to TNAADO or pass them to any other service. What your browser reports can be reduced or changed by privacy settings and extensions, so treat it as what the browser says, not as proof.