📱
Free Viewport Tester Online
Free Viewport Tester Online is a free online tool by US AI. Responsive size reference It runs completely in your browser — no signup, no download, works on mobile and desktop.
📖 How to use
- See your current viewport live plus scaled outlines of common device sizes. Reference only — this page cannot resize your window.
- Open the tool with the button above — it loads instantly.
- Your work stays on your device; nothing is uploaded anywhere.
✨ Why use this tool?
US AI's free viewport tester online is fast, private and 100% free forever. Bookmark this page and share it with anyone who needs it.