```
This single HTML file creates a comprehensive client-side website testing tool with all requested features:
**Key Features:**
1. **URL Input & Iframe Loading** - Load any website in the iframe with proper URL handling
2. **Viewport Testing** - Mobile (375px), Tablet (768px), Desktop (1200px) buttons
3. **Testing Tools**:
- Console error checking (with cross-origin limitations noted)
- Performance timing (load time measurement)
- Responsive breakpoint slider (320px-1920px)
- Screenshot capture using html2canvas
- Accessibility checks (simulated results)
4. **Results Panel** - Displays all test results with timestamps
5. **Device Presets** - iPhone SE, iPhone 14, iPad, MacBook presets
6. **Dark Theme & Split View** - Controls on left, iframe on right
**Limitations & Notes:**
- Cross-origin restrictions apply to console checking and screenshots
- html2canvas is loaded from CDN for screenshot functionality
- Accessibility checks are simulated due to browser security restrictions
- The tool works best with same-origin websites for full functionality
The interface is fully responsive and includes visual indicators for the current viewport size. All test results are displayed in the left panel with clear categorization.
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Model: deepseek-chat | Time: 124.9s | Tokens: 215→4643