Images Drive More Traffic Than Most SEOs Realize
Google Images accounts for roughly 20-25% of all Google searches. That's a massive traffic source that most SEO strategies ignore entirely. And with visual search through Google Lens growing rapidly — over 12 billion visual searches per month — image optimization is becoming more important, not less.
Technical Image Optimization
File Format Selection
- WebP: — Default choice for web images. 25-35% smaller than JPEG at equivalent quality.
- AVIF: — Even smaller than WebP (20%+ reduction), but encoding is slower and browser support is still growing.
- SVG: — For icons, logos, and simple illustrations. Infinitely scalable, tiny file size.
- PNG: — Only when you need true transparency.
Serve format-appropriate images using the picture element:
<picture>
<source srcset="image.avif" type="image/avif">
<source srcset="image.webp" type="image/webp">
<img src="image.jpg" alt="Description of the image content"
width="800" height="600" loading="lazy">
</picture>Responsive Images
Don't serve a 2400px image to a phone screen. Use srcset to let the browser choose the appropriate size:
<img src="image-800.webp"
srcset="image-400.webp 400w, image-800.webp 800w,
image-1200.webp 1200w, image-1600.webp 1600w"
sizes="(max-width: 600px) 400px,
(max-width: 1000px) 800px, 1200px"
alt="Chart showing organic traffic growth over 12 months"
width="1200" height="800" loading="lazy">Always include explicit width and height attributes to prevent Cumulative Layout Shift.
Alt Text That Works for SEO and Accessibility
Good alt text describes what the image shows in a way that's useful if you can't see it.
Good: "Bar chart comparing response times of PostgreSQL, MySQL, and MongoDB for 10,000 concurrent read queries"
Bad: "chart" or "database comparison" or "img_2847.png"
Also bad: "Best database comparison chart showing PostgreSQL vs MySQL vs MongoDB performance benchmarks for database selection optimization" — that's keyword stuffing.
Guidelines: describe what you see, include relevant detail, keep it under 125 characters, and don't start with "image of."
Image Sitemaps
If images aren't discoverable through regular crawling, submit an image sitemap:
<url>
<loc>https://example.com/article-page</loc>
<image:image>
<image:loc>https://example.com/images/diagram.webp</image:loc>
<image:title>System architecture diagram</image:title>
</image:image>
</url>Google Lens and Visual Search
Google Lens identifies objects, text, and scenes in images. As visual search grows, optimizing for it means ensuring your images are clear, well-lit, and contextually relevant.
Use original images — stock photos don't rank well in image search because they appear on thousands of sites. Include text overlays for infographics and annotated screenshots. Ensure images are surrounded by relevant text on the page.
Measuring Image SEO Performance
In Google Search Console, filter the Performance report by "Search type: Image" to see clicks, impressions, and CTR from Google Images. Also check the Discover report — articles with compelling featured images get significantly more Discover traffic.