Responsive Image Checker
Verify if your images use modern responsive attributes (srcset/sizes). Optimize mobile performance and improve Core Web Vitals.
Why Responsive Images Matter
Modern websites are viewed on everything from huge 4K monitors to tiny smartphones. Serving a 4000px wide image to a phone wastes data and dramatically slows down your site.
"Images account for over 50% of typical page weight. Optimizing them with srcset can cut mobile load times in half."
How to Fix Legacy Images
You don't need to manually resize every image. Use the HTML srcset attribute to let the browser choose the best size automatically.
- Add
srcsetattributes with multiple image sizes (e.g., 500w, 1000w). - Use the
sizesattribute to tell the browser which size to use at each viewport. - Always include a fallback
srcand descriptivealttext for accessibility.
Image Format Best Practices
Beyond responsive sizing, choosing the right image format is crucial for performance optimization.
- WebP: 25-35% smaller than JPEG with better quality. Supported by 95%+ of browsers.
- AVIF: Even smaller than WebP but slower to encode. Great for static assets.
- Lazy Loading: Add
loading="lazy"to below-the-fold images to defer loading.
How to Use This Tool
Enter any URL and click "Scan". The tool analyzes all images on the page, checking for responsive attributes like srcset and sizes. Results show a responsiveness score, count of responsive vs legacy images, and a detailed per-image audit with previews.
Frequently Asked Questions
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