Viewport Size Tester
Set a width and height, then preview your pasted HTML sandbox or an embeddable URL in a bounded frame.
A QUICK WALKTHROUGH
How to use this tool
- Set the viewport width and height.
- Paste HTML or an embeddable URL.
- Preview the content and compare the layout at that size.
Safe local preview
Pasted HTML is loaded into a sandboxed local iframe. A URL is used only as an iframe source supplied by you; the tool does not fetch pages itself.
Browser limits apply
External sites can refuse framing with CSP or X-Frame-Options. This preview does not emulate a physical device, browser chrome, network conditions, or bypass access controls.
GOOD TO KNOW
Common questions
Can it test any URL?
Only if the page permits iframe embedding and your browser can load it.
Does it bypass CSP or X-Frame-Options?
No.
Does this emulate a phone or tablet?
No. It sets iframe dimensions only; it does not provide device emulation.