Image alt text is a short written description added to an image’s HTML so screen readers can explain the image to users and search engines can better understand what the image shows. It usually appears in the alt attribute of an image tag.
What image alt text does
Alt text has two main jobs. First, it improves accessibility for people using screen readers or browsing with images turned off. Second, it gives search engines more context about image content, which can support image SEO and reinforce the topic of the page.
Good alt text describes the image clearly and specifically. It should explain what is important about the image in the context of the page, not just list random keywords.
Why image alt text matters for SEO
Search engines cannot interpret images the same way people can. Alt text helps connect the image to the page topic, which can improve relevance signals and help images appear in image search results. It also supports better page quality because accessible websites create a stronger user experience.
For businesses, this matters because product images, service diagrams, screenshots, and blog visuals can all bring in qualified traffic when they are properly labeled. On ecommerce pages, accurate alt text can also help users understand product details if an image fails to load.
How to write effective alt text
Keep it specific and concise
Describe the image in plain language. In most cases, one short sentence or phrase is enough.
Match the page context
Focus on what matters for the page. If the image supports a tutorial, describe the step shown. If it is a product page, include the product name and defining feature.
Avoid keyword stuffing
Do not cram in repeated search terms. Write for people first, then SEO.
Leave decorative images empty
If an image adds no informational value, use empty alt text so screen readers can skip it.
Practical example of image alt text
If a page is teaching beginners how to optimize product pages and the image shows a blue running shoe on a white background, weak alt text would be: “shoe” or “running shoe buy online cheap running shoe.” A stronger version would be: “Blue men’s running shoe with white sole on product page.”
That version is useful because it describes the image accurately, includes relevant detail, and fits the page context without sounding forced. For teams managing many images, create a simple rule: describe what the image shows, mention the key distinguishing detail, and tie it to the page purpose when helpful.