Dashboard
Breakpoint Previewer
Responsive Breakpoint Previewer
Render custom HTML/CSS layouts inside mobile, tablet, and desktop viewports simultaneously for responsive debugging offline.
100% Offline
Business
Layout HTML & CSS Editor
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Frequently Asked Questions
Quick direct-answer guides about using this utility tool locally and securely.
Can I test remote web pages?
Since the previewer runs 100% offline, remote URLs may be blocked by security/CORS configurations. It is recommended to enter your HTML/CSS layout code directly for multi-device previewing.
Does the previewer support responsive Tailwind frameworks?
Yes. Tailwind CDN is automatically injected inside the preview frames, letting you test utility classes in real-time.
Is my code safe when I use the Breakpoint Previewer?
Yes. KuberAgent Breakpoint Previewer runs 100% offline inside your browser — your HTML and CSS code is never sent to any server, stored, or logged anywhere. Everything stays completely private on your device.
Is this breakpoint testing tool free with no signup required?
Yes, it's completely free to use with no account, login, or subscription needed — open the tool, paste your code, and preview instantly.
How do I check if my website looks good on mobile, tablet, and desktop at the same time?
Paste your HTML/CSS into KuberAgent Breakpoint Previewer and it instantly renders your layout across all major screen sizes side by side — mobile (320px–414px), tablet (768px–1024px), and desktop (1280px–1440px) — in a single view without switching devices.
Can frontend developers use this tool to test responsive layouts before pushing code live?
Yes, it's built exactly for this workflow — paste your component or full-page HTML/CSS during development, catch layout breaks across breakpoints instantly, and fix issues before they reach production or code review.
Can I use the Breakpoint Previewer to test HTML email templates across different widths?
Yes, since the tool renders raw HTML and CSS directly, email templates can be tested across different viewport widths to check how the layout responds before sending to subscribers.
Why is my website URL not loading in the Breakpoint Previewer?
Remote URLs are blocked by browser security and CORS policies that prevent external pages from being embedded in iframes. The solution is to paste your HTML/CSS code directly into the tool instead of using a live URL — this always works regardless of the site's security settings.
My layout looks correct on one breakpoint but breaks on another — what should I check?
This usually means a missing or conflicting media query in your CSS. Check that your @media rules cover all target widths, that box-sizing: border-box is set globally, and that percentage-based widths or flexbox/grid rules don't overflow at smaller breakpoints.
How is the Breakpoint Previewer different from Chrome DevTools responsive mode?
Chrome DevTools shows one screen size at a time and requires manual dragging between breakpoints. KuberAgent Breakpoint Previewer renders all breakpoints simultaneously in a single view — making it significantly faster to spot and compare layout differences across devices without any tab switching or resizing.