Responsive Design Tester
Preview HTML at multiple viewport sizes
Responsive Design Tester is a free online tool from BrowserUtils that preview html at multiple viewport sizes. It runs entirely in your browser — your data never leaves your device. No account required.
Device Presets
×
Zoom:
iPhone 14390×844
How to use Responsive Design Tester
- 1 Paste or type your input into the editor above.
- 2 The tool processes your data instantly — right in your browser, with nothing sent to a server.
- 3 Copy the result with one click or continue editing your input.
About Responsive Design Tester
Free online responsive design tester. Preview your HTML content at multiple device viewport sizes including iPhone, iPad, laptop, and desktop resolutions. This tool runs entirely in your browser — your data is never sent to a server. Just paste your input, get instant results, and copy with one click. No sign-up or installation required.
Responsive Design Tester specs
- Runtime
- 100% client-side (browser)
- Built on
- WHATWG URL API and Headers/Fetch standards as implemented by modern browsers
- Cost
- Free — no account, no rate limits, no usage caps
- Browser support
- Chrome 90+, Firefox 88+, Safari 14+, Edge 90+
- Part of
- 299 developer tools on BrowserUtils (100% client-side)
Questions
What device sizes are included?
Preset sizes include iPhone SE (375x667), iPhone 14 (390x844), iPad (768x1024), iPad Pro (1024x1366), Laptop (1366x768), and Desktop (1920x1080). You can also enter custom dimensions.
Can I test external URLs?
Due to browser security restrictions (X-Frame-Options), most external sites cannot be loaded in iframes. This tool is designed for testing your own HTML content pasted directly into the editor.
Can I enter a custom viewport size?
Yes, in addition to the preset device sizes, you can type any width and height in pixels to test your HTML at exact dimensions that match your target viewport.
Does the responsive design tester simulate real mobile behavior?
The tester resizes the viewport to match device dimensions, but it does not simulate touch events, device pixel ratio, or mobile browser quirks. For full device simulation, use browser DevTools or a real device.
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