Use <img> elements with descriptive alt text and filenames; Google doesn't index CSS images

Why it matters

Google calls alt text the most important image attribute and discovers images through the src of <img> elements, including inside <picture>. Background images set in CSS are not indexed. Google's 2026 AI guide also recommends supporting text with relevant images and video for multimodal answers.

How to do it

1. Write alt text that describes the image in the context of the page, without stuffing keywords
2. Rename files like IMG00023.jpg to short descriptive names
3. Use <img> for meaningful images and keep CSS backgrounds for decoration only
4. Add an image sitemap if images are on a CDN or loaded late

Sources

• Google image SEO best practices · Google Search Central, Mar 2, 2026
• Optimizing your website for generative AI features on Google Search · Google Search Central, Jul 10, 2026

Change history

Checked against its sources every Monday. Only content changes are listed.

Related rules

• Rule 17: Write a unique, descriptive <title> per page with the brand at the start or end
• Rule 18: Link to every indexable page with crawlable <a href> links and descriptive anchor text
• Rule 19: Organize pages with one clear H1 and descriptive H2/H3 sections that match real questions