Images often account for the largest portion of a webpage's total size. Properly optimizing images can dramatically improve page load times, user experience, and search engine rankings.

Why Image Optimization Matters

Faster Loading

Users expect pages to load in under 3 seconds

Better SEO

Google uses page speed as a ranking factor

Lower Bounce Rate

53% of users leave if a page takes over 3s

Image Optimization Techniques

1. Choose the Right Format

Select the optimal format based on image content:

•JPEG: Best for photographs - small file size, no transparency
•PNG: Best for graphics with transparency or text
•WebP: Modern format - 25-35% smaller than JPEG
•SVG: Perfect for icons and logos - scalable without quality loss

2. Resize Images Properly

Never upload images larger than their display size. If an image displays at 800px wide, don't upload a 4000px version. Use CSS to scale responsively, but start with the right dimensions.

Pro Tip: For retina displays, use 2x the display size. An image shown at 400px should be 800px for crisp display on high-DPI screens.

3. Compress Images

Always compress images before uploading. Most images can be compressed 50-80% without visible quality loss. Use lossy compression for photographs and lossless for graphics.

4. Use Lazy Loading

Lazy loading delays loading images until they're about to enter the viewport. This significantly improves initial page load time.

<img src="image.jpg" loading="lazy" alt="Description">

5. Implement Responsive Images

Serve different image sizes based on the user's device using srcset and sizes attributes:

<img 
  srcset="small.jpg 400w, medium.jpg 800w, large.jpg 1200w"
  sizes="(max-width: 600px) 400px, (max-width: 1200px) 800px, 1200px"
  src="medium.jpg" 
  alt="Description"
>

6. Use a CDN

Content Delivery Networks (CDNs) serve images from servers geographically closer to users, reducing latency. Many CDNs also offer automatic image optimization and format conversion.

Image SEO Best Practices

Use descriptive filenames: "blue-running-shoes.jpg" instead of "IMG_12345.jpg"

Write alt text: Describe what's in the image for accessibility and SEO

Add structured data: Use schema markup for product images and articles

Create an image sitemap: Help search engines discover all your images

Target File Sizes

Image Type	Target Size
Hero/Banner images	Under 200KB
Content images	Under 100KB
Thumbnails	Under 30KB
Icons	Under 10KB

Conclusion

Image optimization is essential for website performance and SEO. By choosing the right format, properly sizing and compressing images, and implementing modern techniques like lazy loading, you can significantly improve your site's speed and search rankings.

How to Optimize Images for Website Speed and SEO