1. Use a next-gen format (WebP)
Google indexes WebP in Image Search and PageSpeed Insights explicitly recommends it. Converting to WebP is usually the single largest performance win on a page. Do it first; everything else compounds on top.
2. Resize to the displayed size
Never serve a 4000 px image in a 800 px slot. Export at the display width × 2 for Retina at most, and provide srcset so smaller screens download smaller files.
3. Descriptive file names
red-leather-office-chair.webp tells Google what the image shows; IMG_2931.webp does not. Use hyphens, lowercase, and 3–6 words.
4. Write real alt text
Alt text is the primary signal Google Images uses to understand an image and is essential for accessibility. Describe what is in the picture in one sentence; include a keyword naturally if it fits; leave it empty (alt="") only for purely decorative images.
5. Set width and height
Explicit dimensions let the browser reserve space before the image loads, eliminating layout shift (CLS). Modern browsers compute aspect ratio from them, so CSS can still make the image responsive.
6. Lazy-load below the fold, never above
loading="lazy" defers offscreen images. Applying it to the hero image delays LCP; add fetchpriority="high" there instead.
7. Surround images with relevant text
Captions, nearby headings and the page title all help Google understand context. A caption is read far more often than body text, so make it useful.
8. Use structured data
Product, Recipe and Article schema all include an image property. Images referenced in structured data are eligible for rich results and badges in Google Images.
9. Add an image sitemap
Include <image:image> entries in your XML sitemap, especially for images loaded via JavaScript or CSS that crawlers might otherwise miss.
10. Serve from a fast host or CDN
Time to first byte matters for images too. A CDN with long Cache-Control headers and HTTP/2 or HTTP/3 delivers images faster and reduces origin load.
11. Avoid text baked into images
Search engines cannot read text inside an image reliably, and it does not scale on mobile. Use real HTML text over the image instead.
12. Keep originals, publish derivatives
Store PNG/RAW masters privately and publish WebP derivatives. When formats improve again (as AVIF is doing), you can re-export from the master without generation loss.