SEO · 8 November 2025 · 9 min read
Image SEO in 2026: AVIF, alt text, and AI
Image SEO is no longer just alt text. Format, file size, and structured data all matter more in 2026.
Image SEO in 2026 is a four part discipline: format, alt text, structured data, and CDN delivery. Most sites still get only one or two right.
Format
Use AVIF as your default with WebP fallback. PNG only for screenshots that need pixel accuracy. JPEG only for photographs over 800KB where AVIF is not supported.
Alt text
Describe what the image shows in context. Skip "image of". Include the page's primary keyword only when it is genuinely accurate.
Structured data for images
ImageObject schema and correctly labelled product or article images help engines confirm what an image shows and who owns it. This matters for classic image search, but it also feeds AI systems that increasingly cite visual sources alongside text.
- Add ImageObject properties (caption, contentUrl, license) where a CMS field supports it.
- Use descriptive, human readable filenames instead of camera generated strings.
- Keep a consistent licence statement for original photography you are happy to have reused.
- Reference the same image consistently across pages rather than re-uploading duplicates.
Delivery and CDN choices
Format alone does not guarantee speed. How images are resized, cached and served at the edge often matters as much as the file format you choose in the first place.
- Serve responsive sizes with srcset rather than one large file for every viewport.
- Use a CDN or image service that resizes and re-encodes automatically.
- Lazy load everything below the fold, but never the largest contentful image.
- Set explicit width and height attributes to prevent layout shift while images load.
Questions
Support is broad across modern browsers, but a WebP or JPEG fallback is still worth keeping for older devices and some email or PDF contexts.
Only when the keyword genuinely describes the image. Alt text written primarily for keywords rather than accuracy tends to hurt accessibility and trust.
No. It is most useful on hero images, product photography and original photography you want correctly attributed, rather than on every decorative asset.