The Role of Alt Text in Web Accessibility

With more and more technology emerging daily, ensuring that websites and apps are accessible to everyone, including people with disabilities, is essential. Accessibility is not only a legal and ethical responsibility but also a way to enhance user experience for all. One of the fundamental tools for making websites and digital content more inclusive is alt text, short for alternative text. Alt text plays a critical role in providing accessible content, particularly for users who rely on assistive technologies like screen readers.

In this post, we'll explore what alt text is, why it’s necessary, how it should be used, and how to implement alternative text effectively.

What Is Alt Text?

Alt text is a brief description embedded in the HTML code of a website, providing a text-based alternative to images, icons, or other non-text elements. While most users see an image, those using screen readers will hear the alt text description read aloud, allowing them to understand the visual content in a meaningful way.

For example, a visually impaired person browsing a product page may not be able to see the product images, but if each image has descriptive alt text, the screen reader will describe the product to them. Without alt text, the user would miss out on important context that sighted users take for granted.

Why Is Alt Text Necessary?

Alt text is necessary because it makes non-text content perceivable — a key principle of the Web Content Accessibility Guidelines (WCAG). People with visual impairments use screen readers to navigate the web, and without alt text, screen readers can’t interpret or convey the meaning of images.

Moreover, alt text serves multiple functions beyond accessibility. For instance, if an image fails to load due to a poor internet connection, the alt text will still be displayed, ensuring that all users, regardless of device or bandwidth, can access the information. In addition, alt text helps with SEO (Search Engine Optimisation) by providing search engines with a description of the image’s content, improving the visibility of a webpage in search results.

How Should Alt Text Be Used?

Alt text should be applied to any non-text content that conveys essential information. This includes:

Images

Informative images, such as product photos, charts, or diagrams, should include alt text to describe their content.

Icons and Buttons

Any interactive elements, such as buttons or icons (e.g. a magnifying glass for a search function), need alt text that describes their action or purpose. For example, the alt text for a search button should say "Search" instead of simply "Magnifying glass."

Logos

Company logos should have alt text that clearly identifies the company name or brand.

Complex Images

For charts, graphs, or infographics, alt text should summarise the key data. However, if the image is too complex to describe briefly, it’s best to provide a more detailed description on a separate page, while the alt text includes a summary (e.g., "Bar chart showing sales data for 2020-2023. See full description in the link below.").

Not all images need alt text. Decorative images, which don’t add meaning to the page, can be marked with an empty alt attribute (alt="") so screen readers skip over them. This prevents unnecessary clutter for users relying on assistive technologies.

How to Ensure Alt Text Is Effective

Writing effective alt text requires more than simply describing what’s in the image. It’s about conveying the purpose and meaning of the image in the context of the page. Here are some best practices for ensuring alt text is both effective and accessible:

Highlight Key Information

Alt text should succinctly describe the image in a way that conveys its meaning. For instance, instead of writing "A person sitting on a park bench feeding pigeons," a more concise and focused alt text could be "Person feeding pigeons in a park."

Provide Context

Alt text should align with the context in which the image is used. For example, an image of a dog on a veterinary website might use the alt text "Golden retriever getting a checkup at the vet," while the same image on a pet adoption site might use "Golden retriever available for adoption."

Describe Function, Not Just Appearance

For interactive elements, the alt text should describe the function, not just the visual appearance. For instance, if an icon is used as a search button, the alt text should state "Search," not "Magnifying glass."

Consider User Context & Keep it Simple

If the image is accompanied by a caption or surrounding text that already describes its content, there’s no need to repeat that information in the alt text. Instead, you can use a simpler description or an empty alt attribute (alt="").

Use Plain Language

Alt text should be easy to understand. Avoid technical jargon or overly complex sentences. The goal is to make the content accessible to the widest range of users, including those with varying levels of reading comprehension.

Conclusion

Alt text is a simple but powerful tool in ensuring that websites and apps are accessible to everyone. By providing meaningful descriptions of images and other non-text elements, alt text helps people with visual impairments fully engage with digital content. It also enhances user experience across different contexts, whether it’s assisting users with poor internet connections or improving search engine rankings.

For alt text to be effective, it should be concise, descriptive, and context-aware, ensuring that all users can perceive and understand the content. By following best practices, web designers and content creators can make the internet a more inclusive space for all.