Alt Text
What Alt Text Does
Alt text, short for alternative text, is a written description included in an image's HTML via the alt attribute. It's used by screen readers and other assistive technologies to convey the content or function of visual elements to users who are blind or have low vision. When images don't load, browsers may also display this text.
Accessibility Requirements
Alt text is fundamental to accessibility compliance. Under the Web Content Accessibility Guidelines (WCAG), all meaningful images must have accurate text alternatives. This includes WCAG 2.1 Level AA, which is referenced by laws like the ADA, Section 508, and AODA. Failing to provide meaningful alt text creates barriers for users relying on assistive technology and may result in legal risk.
What Images Need Alt Text
Only images that convey important content require alt text. These are known as meaningful images. Examples include charts, infographics, or icons tied to a function. Decorative images—such as borders or purely stylistic visuals—should be hidden from screen readers using empty alt attributes (alt="") or appropriate ARIA roles.
How to Add Alt Text
Adding alt text depends on the tool you're using. Web platforms like WordPress, Wix, and Squarespace typically provide fields to enter alt text during image upload. In PDFs, use Adobe Acrobat Pro's Accessibility tools. In Microsoft Office, right-click an image and choose "Edit Alt Text." Email clients like Outlook or Gmail may offer built-in fields to define alt text for inserted images.
Alt Text and SEO
Alt text also helps search engines understand images since image content can't be crawled directly. Well-written descriptions can improve visibility in image search, potentially driving traffic. However, using unrelated keywords can mislead users and harm both accessibility and rankings. Keyword stuffing in alt text should be avoided.
Best Practices
Describe images clearly, focusing on their role within the page context. If the image performs an action—like a button or icon—describe the function, not just the image. Be concise, as screen readers work best with brief text. Use keywords only when directly relevant.
Alt Text and ADA Compliance
Alt text plays a role in ADA-related accessibility obligations. Courts and federal guidelines look at WCAG standards for determining web accessibility, and meaningful alt descriptions are a common audit point. Ensuring consistent, accurate use of alt text shows attention to user needs and reinforces legal defensibility.