Images are often used to enhance the visual appeal and add additional information in our websites, documents, slides, emails, and social media. When images are not given appropriate alternative text (alt text), people who use screen readers or who have images turned off may miss critical information or context.

Alt text ensures that visual information is available to everyone in a meaningful way. Providing alt text is a core requirement of the Web Content Accessibility Guidelines (WCAG), specifically WCAG 2.x Success Criterion 1.1.1: Non-text Content. This guideline requires that all meaningful non-text content has a text alternative that serves the same purpose.

Tips for writing efffective alternative text include:

• Describe the image clearly and concisely.
• Be specific but brief, focusing on key details.
• Don't start with "image of" or "picture of". The screen reader already announces this.
• Context is kye. Describe what is important based on the purpose of the image.

Examples

Be brief but descriptive. Instead of adding the alt text of simply "Elephants" it is better to say, "A group of elephants near a watering hole at sunset."

Context is key. If this image were part of a real estate or rental website I might say "The Miami Beach Condominiums on Central Avenue." If it were part of an architecture site I might describe it in its architectural context, as "An example of typical, retro art deco style architecture, with salmon and light blue colors and both geometric lines and curves."

If your image contains text, you must include the text as part of the alt text. For example, I might use "A woman sitting cross-legged on the floor surrounded by books, giving a thumbs-up signal with text that reads 'It's cool to learn!'"

If an image is purely decorative and adds no meaningful content for the user, it is best to mark it as decorative if your digital platform gives you that option, or leave the alternative text field blank. This tells the screen reader to skip the image.

If the image is a link, describe the link purpose instead of what is depicted in the image. For example, if this image were on a web page as a static image, I might describe it as "The scales of justice sitting on an open laptop keyboard." If the image serves as a link to a web page, I would put the name of the web page in the alt text field. For example, "Digital Accessibility Legal Blog."

Resources

• Best Practices for Writing Alternative Text for Complex Images (.pdf) from the National Library of Medicine and Georgia Tech.
• DIAGRAM Center's Poet Training Tool is an open source project that provides instruction on when and how to describe images like photographs, drawings, diagrams, charts, etc.
• W3C Alt Text Decision Tree for determining when and how to use alternative text.