Image SEO is the practice of helping search engines find, understand and show a website’s images, so they appear in Google Images, Google Lens and image blocks in ordinary search, and bring visitors back to the site. It covers how images are named, described, placed and made available for crawling.
How image SEO works
Even with its image recognition, Google does not rely on the picture alone. It combines what it sees with the context around the image. The main signals are:
- File name. oak-shaker-kitchen-bromley.jpg tells Google far more than DSC_0193.jpg.
- Alt text. Alt text is a short description of what the image shows, read aloud by screen readers, and the main text attached to the image itself.
- Surrounding text and captions. An image placed next to the paragraph it illustrates, with a caption where useful, is easier to match to searches.
- The page. The page’s title, headings and topic set the context. A good image on a thin page rarely does well.
- Structured data. Product, recipe and article schema markup can connect images to rich results, such as a product photo shown with price and stock.
Google also has to be able to fetch the image. It indexes images placed with the standard HTML img element, including responsive picture and srcset markup, but not images set as CSS backgrounds. Images blocked by robots.txt, or added by scripts Google cannot run, may never be indexed. An image sitemap can help Google discover images it would otherwise miss.
Why it matters
Image search is how many people shop for things they need to see first: furniture, clothing, home improvements, wedding venues, food. Google Lens adds another route, where someone photographs an object and searches with the picture itself. A UK retailer whose product photos show up in those results reaches buyers before they have even typed a brand name.
Image SEO also overlaps with accessibility. Good alt text lets blind and partially sighted visitors understand what an image shows, so getting it right serves people and search engines at the same time. For a service business, original photos of real jobs also build trust in a way stock images cannot.
Common mistakes
- Uploading images with camera-generated file names.
- Writing alt text as a keyword list (“kitchen, kitchens Bromley, best kitchen fitter”) instead of a description.
- Using the same stock photos as competitors, which gives Google no reason to prefer yours.
- Changing image URLs on every redesign or CDN switch, so Google has to find and index them all again.
- Putting headlines, prices or offers inside images, where search engines cannot read them as text.
- Confusing image SEO with file size. Speed belongs to image optimisation; both matter, but they solve different problems.
How to act on it
Begin with the images on the pages that matter most to sales. Rename files before upload, describing the subject in plain words. Write alt text that describes the image for someone who cannot see it, mentioning the product or place where it is genuinely part of the picture. Put each image beside the text it supports, and use your own photographs wherever you can.
Then check the technical side: images use standard HTML, are not blocked in robots.txt, keep stable URLs and, for shops, are included in product structured data. Search Console’s Performance report, with the search type set to Image, shows which pages earn image impressions and clicks. Reviewing images page by page is part of the on-page SEO work I carry out on existing sites.