Image SEO is the practice of helping search engines understand and discover your images so they can appear in image search and support the page they sit on. The essentials are descriptive alt text, sensible file names, standard HTML image elements and relevant surrounding text. This guide focuses on discoverability, not speed, which is covered separately.
Alt text comes first
Google’s image SEO guidance calls alt text the most important metadata for an image. Google uses it together with computer vision and page content to understand the image, and it serves accessibility too. Write descriptive text that fits the context, and avoid keyword stuffing, which Google says may cause a site to be seen as spam.
Good and poor examples for a hypothetical Brisbane bakery product page:
| Weak | Better |
|---|---|
| “bread” | “Sourdough loaf with a dark, scored crust on a wooden board” |
| “best bakery Brisbane sourdough cheap bread buy” | “Sliced rye loaf beside a bread knife” |
| Empty alt on a meaningful photo | Short description of what the photo shows |
The W3C’s alt text decision tree gives a useful rule set. Decorative images, images that repeat nearby text and text shown only for visual effect get an empty alt. Images inside links or buttons should state the destination or action. For a graph or other complex image, keep the alt short and put the detailed information elsewhere on the page.
File names
Use short, descriptive names. Google’s example is that my-new-black-kitten.jpg is better than IMG00023.JPG, and it advises avoiding generic names such as image1.jpg. If you localise images for other languages, Google says to translate the file names too. Rename camera and design-tool exports before upload, and use hyphens between words.
Make images discoverable in the HTML
From the same Google page:
- Use standard img elements with a src attribute. Google does not index CSS background images, so a product photo set as a background will not be seen as an image.
- For responsive images using picture or srcset, always include an img fallback with a src.
- Reference each image with the same URL across pages so Google can cache it.
- Supported formats include BMP, GIF, JPEG, PNG, WebP, SVG and AVIF, and the file extension should match the actual type. Pick the format for the job and keep files light.
- Submit an image sitemap for images Google might not otherwise find. It can list image URLs on other domains, which suits CDNs.
Context on the page
Google advises placing images near relevant text on relevant pages. The words around an image, the headings above it and the page topic all help interpret it. A photo of a service in action on the matching service page carries more meaning than the same photo in a generic gallery. Descriptive internal links to the page also help, which matters most during a website redesign, when image URLs and file names often change by accident.
Choose images worth indexing
Google suggests images that are relevant, high resolution and not extreme in aspect ratio, and recommends avoiding generic logos or images dominated by text. You can influence the preview image with primaryImageOfPage, an image attached to the main entity, or og:image. Structured data can make images eligible for rich results and a badge in Google Images, but the image property is required for that. Original photography and clear illustrations are easier to differentiate than widely used stock files.
A short workflow
- Decide the image’s job: product evidence, explanation, atmosphere or decoration.
- Name the file descriptively before upload.
- Write alt text that describes it in context.
- Place it beside the related text, with a standard img element.
- Add it to an image sitemap if the site loads images in unusual ways.
- Check the rendered HTML to confirm the image and alt text are present.
Limits and trade-offs
Image search traffic is often a small share of the total for service businesses, and ranking is never guaranteed. Optimising images for users, with clear alt text and proper sizing, brings benefits regardless of search. Google also reminds publishers that images are often the largest contributor to page size, so discoverability work should sit beside performance work, not replace it. Images that explain a product also support conversion.
Where Radiance Impact fits
Radiance Impact’s Growth division works on search visibility and SEO. If your site’s imagery is not helping you get found, contact us or see Growth.
Sources
- Google Image SEO best practices, Google Search Central
- Image decision tree, W3C Web Accessibility Initiative
