Online Tool Store
Viewport Size Tester
Preview any embeddable page at common device viewport sizes - iPhone, iPad, laptop, desktop, or a custom width and height. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Some sites block embedding in an iframe (X-Frame-Options) and won't display below - try a page you control if the preview stays blank.
How the viewport size tester works
- Enter the URL of the page you want to preview.
- Choose a device preset or enter a custom width and height.
- View the page rendered at that exact viewport size, scaled to fit.
FAQ
Why can't I see some websites in the preview?
Many sites set the X-Frame-Options or Content-Security-Policy header to block being embedded in an iframe, which prevents the preview from loading - this is a security setting on their end, not a bug in this tool.
What device sizes are included?
iPhone SE, iPhone 14, iPad, a common laptop resolution, and a 1080p desktop - plus a custom option for any width and height you need.
Is this the same as browser dev tools device mode?
It's similar in spirit - a quick way to see a fixed viewport size - but browser dev tools offer more accuracy (real user-agent switching, touch emulation) for serious responsive testing.
Can I test a page I'm developing locally?
Only if it's accessible via a public or network URL - iframes can't load from a file:// path or localhost unless you're viewing this tool from the same machine and it isn't blocked by CORS/frame headers.
How we compare
| Feature | Online Tool Store | Resizing your browser window | Browser dev tools device mode |
|---|---|---|---|
| Exact pixel-precise dimensions | ✓ | ✗ | ✓ |
| No dev tools panel needed | ✓ | ✓ | ✗ |
| Preset common device sizes | ✓ | ✗ | ✓ |
A fast way to eyeball a layout at a specific breakpoint without opening dev tools.