Alt Text Explained: How, When, and Why to Use It for Accessibility

Introduction: What Is Alt Text?

In my professional career as a Senior Quality Assurance Engineer, I always ask about accessibility experience during candidate interviews. Most QA engineers are unfamiliar with accessibility testing, but one of the few checks they often mention is that all images must have alt text. While this is a helpful check and mostly true, I wanted to cover this topic in greater depth and specifically acknowledge that not all images should have alt text. Whether you’re a developer, QA engineer, product owner, or just someone looking to improve your website, this article will dive into what alt text is, how to use it, and when to leave it empty.

Alt text—short for “alternative text”—is an essential attribute added to images in HTML using the alt tag. While invisible to most users, alt text serves a critical role behind the scenes by providing a text description of an image’s content and function. These hidden descriptions allow users who rely on screen readers to perceive and understand images. Alt text ensures everyone can access the information conveyed by images, especially users who are blind or have low vision.

Beyond accessibility, alt text can also impact your site’s SEO. Search engines use alt text to better understand and index images, which can make your images more discoverable in image search results. Additionally, if an image fails to load, the alt text will be displayed in its place, helping users understand what’s missing. With this information in mind, it’s easy for teams to assume that all images should have alt text—otherwise, they risk taking an SEO hit. While not having any alt text is surely a negative for SEO, it’s crucial for teams to understand when an image needs alt text and when it’s okay to leave it blank.

When to Leave Alt Text Empty

While it’s important to provide descriptive alt text for most images, there are situations where leaving the alt attribute empty is not just acceptable, but actually best practice for accessibility. When an image is purely decorative—such as a background flourish, visual divider, or spacer graphic—it doesn’t add meaningful information to the page. In these cases, including a blank alt attribute (alt="") tells screen readers to skip the image entirely, preventing unnecessary distractions for users who rely on assistive technology.

Similarly, if an image is used only for layout purposes, or if it simply duplicates information already provided in nearby text, it’s better to leave the alt text empty rather than repeat yourself. For example, if a product page has multiple identical or very similar images, it’s okay to leave some with empty alt text if this improves the user experience. In many cases, a streamlined experience can be created for assistive technology users by limiting duplicate information and reducing verbal clutter.

Tips for Writing Good Alt Text

• Be descriptive and specific. Go beyond generic terms, and describe exactly what’s in the image and why it matters. For instance, instead of simply writing “sign with dog,” your alt text should communicate the warning message and the visual cues that the sign conveys. A strong alt text for an image of a sign that says “Danger, Dog!” and includes a picture of a snarling dog might be:
  “Warning sign reading ‘Danger, Dog!’ with image of a growling dog showing its teeth.”
  This level of detail ensures users who rely on screen readers understand both the written and visual warnings being conveyed, helping them fully grasp the intent and urgency of the sign.
• Keep it concise but complete. Aim for a clear, focused description in a single phrase or sentence—generally under 125 characters. Include essential details, but avoid long, complex sentences that could overwhelm users of assistive technology. Also, avoid redundant phrases like “image of” or “picture of,” since screen readers already identify images to their users.
• Use context from the page. Consider how the image supports the surrounding content and what information it adds for the user. Ask yourself: “What does the user need to know from this image in this context?” For instance, if an image shows a red warning icon next to an error message, the alt text could be “warning icon” or “red exclamation mark,” since the error is explained in the text.
• Don’t keyword stuff. Use natural, reader-friendly language. Including excessive keywords (“SEO, marketing, sales, analytics, business chart, graph...”) makes alt text less helpful and can hurt accessibility. Focus on clarity and usefulness, without being overly verbose.
• Describe color only when relevant. If color conveys important information (like in charts or colored status indicators), mention it: “Red bar showing decline in sales.” Otherwise, leave out color details for purely decorative or non-informative images.
• Write meaningful alt text for logos. If the logo represents the company, use the brand name as alt text (e.g., alt="Coca-Cola"). If it’s purely decorative or repeated elsewhere, use alt="".
• Summarize infographics and complex images. For graphs, diagrams, or infographics, provide a concise summary in the alt text, and offer a longer, detailed description nearby if needed. Example:
  alt="Pie chart showing 40% of users prefer dark mode, 60% prefer light mode. See full data below."
• Skip decorative images. If an image serves no informational or functional purpose—such as a background pattern, divider, or decorative flourish—use an empty alt attribute (alt=""). This helps screen readers skip irrelevant content and optimizes the user experience.
• Don’t repeat yourself. If the image’s content is already explained in a caption, heading, or button label, don’t restate it in the alt text. This reduces redundancy and makes the experience smoother for screen reader users. Also, don’t repeat the same alt text multiple times. If you find you have the same alt text multiple times on a page, this is a clear sign to audit the user experience for duplicate content.
• Describe function for actionable images. For buttons, icons, or linked images, explain their action: use alt text like “Search,” “Download PDF,” or “Submit form,” rather than just describing the image’s appearance.
• Review alt text manually. Automated tools can flag missing alt text but can’t judge quality, context, or clarity. Always review your alt text to ensure it’s accurate, helpful, and meaningful for your site’s real users.

How Can You Improve Your Alt Text?

Alt text quality is a shared responsibility across product owners, developers, and QA testers. Here’s how each team member can contribute to more accessible and user-friendly websites:

Managing Alt Text for Product Owners: Product owners are responsible for ensuring that every image on their site has meaningful and appropriate alt text. Developing a clear strategy for creating, organizing, and regularly updating alt text is essential—especially for sites with a large or dynamic image library. Consider leveraging content management systems (CMS), modern databases, or dedicated digital asset management tools to store and manage alt text consistently. Product owners should also provide clear guidelines and empower team members—such as designers, writers, and developers—to select and use images with accurate alt text, or to request alt text when it’s missing.

Handling Alt Text for Developers: While developers play a key role in implementing alt text in code, they are not typically responsible for writing the alt text for every image. Instead, developers should focus on building flexible systems that allow content editors or product owners to add or update alt text easily. This includes supporting both descriptive alt text and empty alt attributes for decorative images, and ensuring that image components or templates can accommodate all necessary accessibility attributes. Developers should also communicate with other team members when alt text is missing or unclear, and help enforce best practices through code reviews and documentation.

Testing Alt Text for QA: During QA and testing, it’s crucial to verify that images use alt text appropriately throughout the user experience. This means checking not only for the presence of alt text, but also its accuracy and relevance. Automated accessibility tools can quickly flag missing alt attributes, but manual review is needed to assess the quality and context of each alt text entry. QA testers should pay special attention to distinguishing between functional images (which need descriptive alt text) and decorative images (which should use empty alt attributes). Common issues to watch for include missing alt text, duplicate alt text, and opportunities for improvement in clarity or specificity. All findings should be communicated to the team so they can be addressed before launch.

Conclusion

Handling alt text is a small issue that makes a big difference on your site. Thoughtfully written alt text makes your website more accessible, inclusive, and user-friendly for everyone. It also helps improve your site’s SEO and ensures your content is discoverable, regardless of how it’s accessed by users.

Remember, effective alt text is a team effort. Product owners should establish clear strategies and guidelines, developers should build accessible systems, and QA testers should regularly verify that images are handled appropriately. By working together and following best practices, your team can create a web experience that works for all users.

Take time to regularly review and update your alt text, and don’t hesitate to leverage both automated tools and manual checks as part of your ongoing accessibility efforts. With these steps, you’ll not only meet compliance standards but also show a true commitment to digital inclusion in your organization.