Responsive Breakpoint Previewer
Load a chosen website in sandboxed frames at 375, 768, 1024 and 1440 CSS pixels wide, each 640 pixels high.
Ready. No website requested.
Frames are scaled to fit each card; their CSS viewport sizes stay fixed. This is not device, touch or pixel-density emulation.
Direct website requests: Loading contacts the chosen website directly. Cookies follow browser policy. Scripts can run, but forms, popups and storage-dependent features may be blocked by the sandbox. No backend fetch, proxy or screenshot is used.
Embedding and address limits: CSP or X-Frame-Options can block embedding. The tool cannot bypass them, inspect frame contents or confirm visibility from a load event. Local hosts, private IP literals and this app origin are rejected; DNS results and redirects are not verified.
CSS viewport: 768 × 640 CSS px
CSS viewport: 1024 × 640 CSS px
CSS viewport: 1440 × 640 CSS px
A QUICK WALKTHROUGH
How to use this tool
- Enter a complete public HTTPS URL without credentials.
- Click Load to request the website in four frames.
- Compare layouts; edit the URL and click Load or Reload to request again.
Direct website requests
Loading contacts the chosen website directly. Cookies follow browser policy. Scripts can run, but forms, popups and storage-dependent features may be blocked by the sandbox. No backend fetch, proxy or screenshot is used.
Embedding and address limits
CSP or X-Frame-Options can block embedding. The tool cannot bypass them, inspect frame contents or confirm visibility from a load event. Local hosts, private IP literals and this app origin are rejected; DNS results and redirects are not verified.
GOOD TO KNOW
Common questions
Why is a frame blank?
The site may block embedding, fail to load or rely on sandbox-restricted features. A load event does not prove the site is visible.
Does this emulate a phone?
No. It only sets CSS viewport dimensions. Device pixel ratio, touch, browser chrome and network conditions are unchanged.