Image SEO + Alt Text for AI Overview Citations

TL;DR

• AI engines now read images + alt text + caption + surrounding paragraph as one citation candidate.
• The right alt text is descriptive of the image content plus the page topic — not stuffed with keywords.
• WebP at 80-85% quality is the right format for SEO + Core Web Vitals balance.
• Captions below images are read more reliably than alt text by AI engines.
• Image schema (ImageObject) on hero images doubles citation rate.

The right alt text format

Pattern: [what's in the image], [page topic context]

Bad: seo or digital marketing image or empty alt Good: Diagram of an AEO content structure with TL;DR and FAQ blocks (specific + topical)

Captions matter more than you think

A caption rendered visibly below the image is read as canonical text by AI engines. Hidden alt text is read but with lower confidence.

Schema for images

{
  "@type": "ImageObject",
  "url": "https://atil.ltd/blog/image.jpg",
  "caption": "AEO content structure",
  "creditText": "ATIL",
  "creator": {"@type": "Organization", "name": "ATIL"},
  "license": "https://atil.ltd/license"
}

File optimisation

• Format: WebP (fallback to JPEG)
• Quality: 80-85% (Q92 for hero/portfolio images)
• Width: 1200px max for full-width content
• File name: descriptive, hyphenated (amazon-acos-reduction-chart.webp)
• Lazy-load below the fold
• width and height attributes set to prevent CLS

FAQ

Does empty alt text get penalised?

No — but it loses the citation opportunity.

Should every image have alt text?

Decorative images can use alt="" (intentionally empty).

What about animated GIFs?

Convert to MP4 or WebM — better compression, better SEO.

Does Bing Visual Search matter?

Yes — increasing weight, especially for ChatGPT image queries via Bing.

Next

Free SEO audit — we check image SEO across your site.

Related: Schema markup AI engines actually read · Page experience signals 2026