What are alt tags and why are they important?

Alt tags is the common shorthand for alt text in an image’s alt attribute. Alt text describes the content or purpose of an image when the image is not visible, is read by screen readers or is interpreted by search engines. Strictly speaking, the important technical part is the ALT attribute in the HTML code.

Alt text is a small technical detail, but it matters for web accessibility, image understanding and editorial quality.

Why alt text matters

Alt text serves several purposes:

• screen readers can communicate the image content or purpose
• users get a text alternative if images do not load
• search engines receive context about the image and page
• decorative images can be marked as irrelevant
• linked images receive a meaningful link purpose

The W3C Web Accessibility Initiative provides an alt decision tree for deciding what kind of alt text is appropriate.

What makes good alt text?

Good alt text does not describe every pixel. It describes the relevant meaning of the image in the context of the page. For a product photo, the product may matter. For an infographic, the essential information must be available in text. For purely decorative visuals, an empty alt="" can be appropriate so screen readers skip the image.

Weak alt text includes keyword stuffing, file names, generic words like “image” or descriptions without context. Good alt text is concise, specific and useful.

Alt tags, SEO and website quality

For search engine optimization, alt text is not a magic ranking factor, but it is an important quality signal. It supports image search, topical understanding and accessibility. Together with image optimization, meaningful file names, modern image formats and clear page structure, it contributes to a professional website.

For large websites, a systematic audit is useful: Are alt texts missing? Are they duplicated? Do they actually describe the content? Relaunches, shops and blog archives often contain many small issues that can be improved.