Image SEO

Image SEO is the practice of optimising images so they load quickly, are understood by search engines and can appear in Google Images and other visual search features. Well-optimised images improve Page Speed, accessibility and the overall quality of a page.

Written by Paul Hoda, SEO consultant since 2005. Last updated 8 November 2026.

Why image SEO matters

  • Speed: images are often the largest files on a page and the most common cause of slow LCP.
  • Extra traffic: Google Images, image packs in normal results and Google Lens can send visitors.
  • Context: images help Google understand the topic of a page, especially products, places and visual content.
  • Accessibility: descriptive alt text makes images usable for people with screen readers.
  • Rich results and AI: product, recipe and article images can appear in rich results and AI answers.

Image SEO best practices

  1. Use original images where possible. Real photos of your work, team, products and premises build trust and stand out more than stock images.
  2. Choose the right format. Use WebP or AVIF for photos, SVG for logos and icons, and PNG only when you need transparency in detailed graphics.
  3. Resize images to the largest size they will be displayed at; do not upload a 4000-pixel image to show at 800 pixels.
  4. Compress images to reduce file size without visible quality loss.
  5. Serve responsive images with srcset so phones get smaller files.
  6. Name files descriptively, such as technical-seo-audit-report.webp rather than IMG_4821.jpg.
  7. Write helpful Alt Text describing what the image shows.
  8. Set width and height attributes to prevent layout shifts (Cumulative Layout Shift (CLS)).
  9. Lazy-load images below the fold with loading=”lazy”, but not the main hero image.
  10. Place images near relevant text, with captions where helpful; captions are among the most read text on a page.
  11. Use a CDN to deliver images quickly worldwide.

Structured data and image sitemaps

Include images in your Schema Markup for articles, products, recipes and organisations so Google can use them in rich results. If many important images are loaded in unusual ways, an image sitemap can help Google discover them.

Images and E-E-A-T

Photos that show real experience, such as before-and-after results, project photos or team members at work, support E-E-A-T far better than generic stock imagery. For reviews and case studies, original images are strong evidence that you have actually done what you describe.

AI-generated images

AI images can be useful for illustrations and concepts, but avoid using them to depict real products, people or results, which can mislead visitors. Label them where appropriate and still optimise their size, format and alt text.

Common image SEO mistakes

  • Huge, uncompressed images slowing pages down.
  • Missing or keyword-stuffed alt text.
  • Important text embedded inside images, where search engines and screen readers struggle to read it.
  • Lazy-loading the hero image.
  • Images blocked in robots.txt.
  • Using CSS background images for important content images, which Google indexes less reliably.

On WordPress, image optimisation plugins can automate compression, WebP conversion and lazy loading, but always check that the hero image is excluded from lazy loading.

Further reading: Google’s image SEO best practices.

Key Takeaways

  • Optimised images load faster and can rank in Google Images.
  • Use modern formats, correct sizes and compression.
  • Write descriptive file names and alt text.
  • Set width and height and lazy-load only below-the-fold images.
  • Original photos support trust better than stock images.

Related Terms

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