Images account for an average of 50% of a web page's weight and represent an SEO opportunity that is often underexploited. In 2026, Google indexes and ranks images via Google Images, but also through universal search where image results appear directly in the SERPs. A well-optimised image generates additional traffic and improves performance signals that influence the ranking of the entire page.
1. Name your image files correctly
The image file name is one of the first signals Google uses to understand the content of an image. A descriptive and relevant file name directly improves visibility in Google Images.
- Use descriptive keywords separated by hyphens: running-shoes-men-nike.webp rather than IMG_4821.jpg
- Keep it concise — 3 to 5 words maximum is sufficient
- Do not use special characters, spaces or capital letters
- The file name should match the actual content of the image
2. Write effective alt tags
The alt tag (alternative text) is the most important SEO signal for an image. It serves two purposes: allowing search engines to understand the content of the image, and providing a description for visually impaired users using a screen reader.
- Accurately describe what the image shows in natural language
- Include the main keyword of the page if it is naturally relevant — never forced
- Limit yourself to approximately 125 characters
- Never write "image of" or "photo of" — start directly with the description
- Leave the alt attribute empty (alt="") for purely decorative images
Good to know: Google can now analyse the visual content of an image thanks to its computer vision technology (Google Lens). An alt tag consistent with the actual image content reinforces this signal. Conversely, an alt tag that does not match the image may be considered spam and penalise your SEO.
3. Choose the right image format
The image format directly influences load time, which is a ranking factor. In 2026, the recommended formats are:
| Format | Recommended use | Advantages |
|---|---|---|
| WebP | Photos, illustrations, content images | 30% lighter than JPEG, transparency supported |
| AVIF | High-quality photos | 50% lighter than JPEG, better quality |
| SVG | Logos, icons, vector illustrations | Infinitely scalable, very lightweight |
| PNG | Images requiring transparency or sharp text | Lossless, but heavy |
| JPEG | Universal legacy compatibility | Compatible everywhere, but heavier than WebP |
4. Compress images without visible quality loss
Compression reduces image weight without perceptible degradation, which speeds up page loading and improves LCP (Largest Contentful Paint), a Core Web Vitals signal integrated into Google's ranking factors.
- Squoosh (squoosh.app): free online tool by Google to compress and convert to WebP/AVIF
- Sharp: Node.js library for automated server-side compression
- ImageMagick: powerful command-line tool for batch processing
- TinyPNG / TinyJPG: simple online compression for PNG and JPEG
As a general rule, aim for a weight below 200 KB for standard content images and below 100 KB for blog or article images.
5. Implement responsive images with srcset
Serving a 2000px image to a mobile user displaying 400px wide is a waste of bandwidth that penalises loading. The srcset attribute allows automatically serving the size suited to the device.
- Generate multiple versions of each image (400px, 800px, 1200px, 1600px)
- Declare them via the srcset attribute and the sizes attribute to guide the browser
- Google takes into account the actually loaded size to evaluate mobile performance
Good to know: since 2021, Google uses Mobile-First indexing — the mobile version of your page is the one analysed and ranked as a priority. Correctly sized images for mobile are therefore essential, not only for performance but also for SEO ranking.
6. Create and submit an image sitemap
An image sitemap allows Google to discover images that might otherwise not be indexed — particularly images loaded via JavaScript or images hosted on an external CDN. It can be integrated into the main sitemap or constitute a dedicated file.
- Use the <image:image> tag in your XML sitemap
- Include the URL, title and caption of each image
- Submit the sitemap via Google Search Console
- CMS platforms like WordPress automatically generate image sitemaps via plugins like Yoast SEO or Rank Math
7. Use structured data for images
Structured data (Schema.org) allows Google to associate an image with a specific context — product, recipe, article, person. This can trigger rich snippets in search results with a visible image thumbnail.
- For an article: use the Article type with the image property
- For a product: use the Product type with the image property
- For a recipe: the Recipe type with image systematically generates a thumbnail in results
- Validate your structured data via Google's Rich Results Test
8. Host images on a trusted domain with HTTPS
Images hosted on unsecured third-party domains (HTTP) can trigger mixed content warnings in the browser and harm the trust Google grants to your page. In 2026, HTTPS is an absolute prerequisite for any indexed image.
Good to know: using a CDN (Content Delivery Network) to host your images offers a dual SEO advantage: reducing loading latency through the geographic proximity of servers, and offloading the main server which can thus respond more quickly to HTML requests. These two combined effects improve TTFB and LCP, two metrics directly linked to Google ranking.