Responsive Website Tester
Preview any website on multiple screen sizes simultaneously. Faster than browser DevTools.
📖 Complete Guide to Responsive Website Testing
In today's multi-device world, your website must work flawlessly across smartphones, tablets, laptops, and desktop monitors. With mobile devices accounting for over 55% of global web traffic and Google using mobile-first indexing, responsive design isn't optional—it's essential. Our Responsive Website Tester lets you preview any website across multiple screen sizes simultaneously, dramatically faster than manually resizing your browser.
Traditional responsive testing involves repeatedly resizing your browser window or cycling through device presets in browser DevTools. This process is slow, disruptive to your workflow, and makes it difficult to compare how a page looks across multiple sizes at once. Our tool loads your website in multiple viewports simultaneously, giving you an instant overview of responsiveness without the back-and-forth.
📱 Understanding Device Presets
Our tool includes four carefully chosen device presets that represent the major breakpoints in responsive design:
| Device | Dimensions | Represents | Common Breakpoint |
|---|---|---|---|
| 📱 Mobile | 375 × 667 | iPhone SE, iPhone 8, similar Android phones | < 576px (Bootstrap XS) |
| 📱 Tablet | 768 × 1024 | iPad (portrait), Android tablets | 576px - 992px (Bootstrap SM/MD) |
| 💻 Laptop | 1366 × 768 | Most common laptop resolution worldwide | 992px - 1200px (Bootstrap LG) |
| 🖥️ Desktop | 1920 × 1080 | Full HD monitors, most common desktop resolution | > 1200px (Bootstrap XL) |
🎛️ View Mode Options
Three layout options let you customize how the device previews are displayed:
- Grid View: Shows all enabled devices in a responsive grid layout. Best for getting a quick overview of how your site looks across all screen sizes simultaneously. The default and most commonly used view.
- Stack View: Arranges devices vertically in a single column. Useful when you want to scroll through devices one by one, or when working on a narrow screen where grid layout is cramped.
- Focus View: Shows one device at a time at larger scale with navigation buttons to switch between devices. Best for detailed examination of specific viewport behavior.
🔧 Device Controls
Each device frame includes controls for individual manipulation:
| Control | Function | Use Case |
|---|---|---|
| 🔄 Rotate | Swaps width and height dimensions | Test portrait vs landscape orientation |
| ↻ Refresh | Reloads the page in that specific viewport | Test loading states, reset after interaction |
| ↗ Open | Opens the URL in a new browser tab | Use when iframe embedding is blocked |
➕ Custom Device Sizes
The Custom Device feature lets you test any specific dimensions you need. This is invaluable for:
- Specific Device Testing: Test exact dimensions of devices your audience uses (check your analytics for popular resolutions)
- Breakpoint Debugging: Test dimensions just above and below your CSS breakpoints to catch edge cases
- Unusual Aspect Ratios: Test ultra-wide monitors, folding phones, or embedded displays
- Client Requirements: When a client specifies particular device requirements, test those exact sizes
⚠️ Important: Some websites block iframe embedding using security headers (X-Frame-Options or Content-Security-Policy). This is a security feature, not a bug. Major sites like Facebook, Twitter, banking sites, and many e-commerce platforms block embedding. If a site won't load, use the "Open in new tab" button to view it directly, or test in browser DevTools instead.
🚀 Why Use This Over Browser DevTools?
Browser DevTools are excellent for debugging, but our tool excels at visual comparison:
- Simultaneous Comparison: See all viewports at once instead of switching between them one at a time
- Faster Workflow: No need to repeatedly resize, screenshot, or toggle device emulation
- Client Presentations: Show clients their site across devices in a single view
- Design Review: Designers can quickly assess responsive behavior without technical knowledge
- Team Collaboration: Share URLs with query parameters to show specific configurations
For detailed CSS debugging, DOM inspection, or network analysis, DevTools remains the better choice. Our tool complements DevTools for the visual comparison aspects of responsive testing.
❓ Frequently Asked Questions
Many websites set security headers that prevent them from being embedded in iframes—this is actually good security practice. X-Frame-Options and Content-Security-Policy headers can block embedding to prevent clickjacking attacks. Sites like Facebook, Twitter, Instagram, most banking sites, Google services, and many e-commerce platforms block iframe embedding. When this happens, you'll see an error or blank frame. Use the "Open in new tab" button to view these sites directly, or test them using browser DevTools device emulation instead. Our tool works best for testing your own websites and sites that allow embedding.
They serve different purposes. Our tool excels at quick visual comparison across multiple viewports simultaneously—you can see mobile, tablet, laptop, and desktop all at once. DevTools is better for detailed debugging: inspecting elements, modifying CSS live, analyzing network requests, testing specific device characteristics, and simulating network conditions. For designers and stakeholders who need to assess overall responsive behavior quickly, our tool is faster. For developers debugging specific CSS issues, DevTools provides more control. Ideally, use both: our tool for overview and comparison, DevTools for detailed investigation.
Yes! Enter your localhost URL (like http://localhost:3000 or http://127.0.0.1:8080) and it will work as long as your local development server is running. This is excellent for testing during development before deploying. Note that localhost testing only works on the same computer—you can't test someone else's localhost. Also ensure your development server doesn't set X-Frame-Options headers that would block embedding. Most development servers (Create React App, Vue CLI, Next.js dev mode, etc.) allow iframe embedding by default.
Yes, the iframes are set to the exact pixel dimensions specified. Your website receives accurate viewport dimensions and will trigger the correct CSS media queries. However, the visual display on your screen is scaled down to fit the available space—you'll see a percentage indicator showing the scale (e.g., "60%"). This scaling is purely visual; the website itself "believes" it's at full size. One limitation: we can't accurately simulate device-specific features like touch events, device pixel ratio (Retina displays), or mobile browser chrome (address bar, navigation). For those tests, use actual devices or browser DevTools.
Yes, the previews are fully functional iframes. You can click links, fill out forms, and interact with the page just like you would in a regular browser window. However, keep in mind: navigation within the iframe only affects that specific viewport, JavaScript may behave differently in iframe context due to security restrictions, some features like geolocation or camera access may not work in embedded frames, and cookies and localStorage may be isolated from the main site. For testing complex interactions, the "Open in new tab" button provides a better experience.
Use the Custom Device feature to create viewports at your exact breakpoint boundaries. For example, if your CSS has a breakpoint at 768px, create custom devices at 767px and 769px to see how your layout behaves just below and just above the breakpoint. This helps catch edge cases where elements might jump awkwardly or where there's a visual glitch right at the breakpoint. Common breakpoints to test: 575px/576px (Bootstrap sm), 767px/768px (Bootstrap md), 991px/992px (Bootstrap lg), and 1199px/1200px (Bootstrap xl).
Why Ads?
Ads help keep DC Tools free and running. Thank you for your support!
Found a Bug?
Help us improve! Report issues and suggestions.