What is image SEO?

Image SEO, explained

Google's image SEO guidance starts with discovery: use standard HTML <img> elements, because they help crawlers find and process images, and consider an image sitemap for images Google might miss. Google Images supports BMP, GIF, JPEG, PNG, WebP, SVG and AVIF.

Then context. Google uses the page's content, title and headings, the image's filename, alt text and nearby text to work out what an image shows. Descriptive filenames like search-console-performance-report.webp beat IMG_4432.png. Put images near the text they illustrate. Google also lets you signal a page's preferred image with the primaryImageOfPage property or an og:image tag, which helps Google choose the right image for the page. It also favors high-quality, relevant images over blurry ones or generic logos.

Then performance. Large images are the most common cause of slow Largest Contentful Paint. Serve modern formats like WebP or AVIF, size images for the space they fill, use srcset or <picture> for responsive versions, set width and height to prevent layout shift, and lazy-load below-the-fold images while loading the hero eagerly.

For most SaaS products, image search isn't a major traffic source, but screenshots and diagrams still appear in regular results, in AI answers and in link previews. For design tools, templates, recipes or ecommerce, it can be a real channel.

Why it matters for founders

Images affect speed on every page and can bring traffic on their own. Most of the work is setting good defaults once in your image component.

Example

Your blog uses 2MB PNG screenshots named Screen Shot 2026…png. You switch to compressed WebP files with descriptive names, explicit dimensions and useful alt text, and pages load faster.

Common mistakes

• Huge PNG screenshots served at full size.
• Images without width and height, causing layout shift.
• Generic filenames and empty alt text.
• Lazy-loading the hero image.