Image alt text, also known as the alt attribute or alternative text, is a description added to an HTML image tag. Alt text plays a critical role in web accessibility by allowing screen readers to describe images to visually impaired users. It also enhances SEO by helping search engines understand the content and purpose of images. In this article, we’ll discuss what alt text is, why it’s important, common mistakes to avoid, and best practices for writing effective alt text.
Image alt text is an HTML attribute used within an img tag to provide a text description of an image. The text is read aloud by screen readers, allowing visually impaired users to understand the image’s content. If an image fails to load, the alt text also appears in its place, helping all users understand what the image represents.
<img src="dog-playing.jpg" alt="A golden retriever playing fetch in a grassy park">In this example, the alt text describes the image, making it accessible to users who can’t see it and providing search engines with information about the image’s content.
Alt text allows screen readers to describe images, making content accessible to visually impaired users. Accessible images help websites meet Web Content Accessibility Guidelines (WCAG).
Search engines use alt text to understand image content, which can improve a site’s SEO. Well-written alt text provides context, helping search engines index images properly and improve search ranking.
When images don’t load due to slow connections or errors, the alt text appears in place of the image, providing context for users even if the image is unavailable.
Many accessibility laws, including the ADA in the U.S., require alt text on images to ensure digital accessibility for users with disabilities.
Descriptive alt text enhances user experience by ensuring that all users, regardless of their abilities, have access to the same information and context.
Omitting alt text deprives visually impaired users of important context. Use descriptive alt text for all informational images.
Avoid starting alt text with phrases like “image of” or “picture of.” Screen readers already announce it as an image, so redundant wording isn’t necessary.
While SEO benefits from alt text, avoid overloading it with keywords. Keyword stuffing can make alt text confusing for users and can be penalized by search engines.
Decorative images that don’t add meaningful information should use empty alt text (alt="") so screen readers skip over them. This allows users to focus on relevant content.
Alt text should be specific. Generic text like “photo” or “image” doesn’t provide meaningful information to users or search engines.
Describe what’s in the image in a clear, concise way. Include details that provide context or convey the purpose of the image.
<img src="chocolate-cake.jpg" alt="A slice of chocolate cake with whipped cream and a cherry on top">If relevant, include a keyword naturally within the description, but avoid keyword stuffing. Focus on describing the image first, with keywords as a secondary priority.
Aim to keep alt text between 5 and 15 words. Screen readers read alt text aloud, so short, descriptive text helps users without overwhelming them.
Write alt text based on the context of the image within the content. For example, if an image of a laptop appears in an article about working from home, the alt text could be, “A laptop on a desk by a window, ideal for remote work.”
If an image is purely decorative, use an empty alt attribute (alt=""). This tells screen readers to skip the image, keeping the focus on essential content.
<img src="decorative-border.jpg" alt="">Alt text should be detailed but concise. Avoid overly long descriptions that may become tedious for screen reader users. For complex images, such as charts or infographics, consider adding a full description elsewhere on the page.
This alt text describes the image in a way that conveys context and relevance.
<img src="team-meeting.jpg" alt="A diverse group of people in a team meeting, discussing a project">This is too vague, lacking context and specific information about the image content.
<img src="team-meeting.jpg" alt="Image of people">Descriptive and relevant, capturing the visual elements that make the image meaningful.
<img src="mountain-sunset.jpg" alt="Sunset over the Rocky Mountains with pink and orange clouds">This is generic and doesn’t convey the specific visual elements in the image.
<img src="mountain-sunset.jpg" alt="Beautiful view">Alt text is essential for meeting WCAG standards, which are often required for legal compliance. Alt text ensures that visually impaired users can engage with image content.
Alt text contributes to SEO by providing search engines with relevant information about image content. When images have optimized alt text, they are more likely to appear in search results.
By providing meaningful context, alt text improves the user experience, encouraging engagement and retention.
Alt text helps users understand visual elements even when images fail to load, enhancing content comprehension and reducing potential confusion.
Effective image alt text is essential for creating an accessible, SEO-friendly website. By writing clear, descriptive alt text that provides context and avoids redundant or vague language, you can enhance accessibility for visually impaired users and improve search engine visibility. Optimizing alt text is a simple but impactful way to make your site more inclusive, SEO-friendly, and user-centered.