Mastering Alt Text for Images: A Step-by-Step Guide

In web development, accessibility is a crucial aspect of creating an inclusive online experience. One of the easiest and most effective ways to improve accessibility is by correctly using the alt attribute for images. The alt (alternative text) provides a textual description for images, ensuring that users with visual impairments can understand the content.

However, figuring out when and what to include in the alt attribute can be tricky, given the wide variety of images and their different purposes. In this guide, we’ll walk you through a decision tree that will help you understand how to use the alt attribute in different scenarios, ensuring your website is accessible and user-friendly for everyone.

Why is the Alt Attribute Important?

Before we dive into the decision-making process, let’s briefly cover why the alt attribute is so important. The alt text serves multiple purposes:

Screen readers: For users who rely on assistive technology to navigate the web.
SEO: Search engines use alt text to index images and understand the content of your page.
Connectivity: Users with slow internet connections may disable images, and alt text helps them understand the content of the page.

By using the alt attribute correctly, you help make your site more accessible, improve your SEO, and ensure that all users can interact with your content.

The Alt Decision Tree: A Simple Guide for Developers

Let’s break down a decision tree to help you determine when and how to use the alt attribute for different types of images.

Does the Image Contain Text?

Yes:

And the text is also present as real text nearby:
Use an empty alt attribute. If the text in the image is also visible in the surrounding content, there’s no need to repeat it. For example, a logo with a company name nearby doesn’t need alt text.
And the text is only shown for visual effects:
Use an empty alt attribute. If the text is purely for design purposes (such as an image used to style a heading), there’s no need to describe it.
And the text has a specific function, like an icon:
Use the alt attribute to describe the function of the image. If the image is an icon (e.g., a shopping cart), the alt attribute should describe its purpose: alt="Add to cart".
And the text in the image is not found elsewhere:
Use the alt attribute to include the text. If the text in the image is unique (like a quote or specific phrase), include it in the alt text.

No (The image doesn’t contain text):
Move to the next step.

Is the Image Used in a Link or a Button, and Would It Be Difficult to Understand What the Link or Button Does Without the Image?

Yes:
Use the alt attribute to describe the action or destination. For example, if the image is a button (like a “submit” icon), the alt should describe what happens when clicked: alt="Submit".
No:
Continue to the next question.

Does the Image Add Meaning to the Page or Context?

Yes:
And it’s a simple graphic or photo:
Provide a brief description of the image in the alt text. For example, a photo of a beach might have the alt text alt="A sunny beach with sand and waves". The key is to communicate the meaning of the image concisely.
And it’s a complex graphic, like a chart or graph:
Provide the information elsewhere on the page. For graphs or charts, you should describe the key points in the text nearby, as alt text alone may not capture the full meaning.
And the image is redundant to nearby text:
Use an empty alt attribute. If the image repeats information that is already conveyed in surrounding text, there’s no need to include alt text. For example, a chart with a caption that explains the data doesn’t need additional descriptions in the alt attribute.
No:
Move on to the next question.

Is the Image Decorative or Not Meant to Convey Information?

Yes:
Use an empty alt attribute. Decorative images, such as background patterns or borders, don’t need to be described. Screen readers will ignore these images if you leave the alt attribute empty.
No:
Continue to the next step.

Does the Image’s Use Fall into One of the Categories Above or Is It Unclear What Alt Text to Provide?

If you find that your image doesn’t fit into any of the categories above, it might be a bit tricky to determine the correct alt text. In such cases, it’s best to consult detailed guidelines, like the Images Tutorial, to decide the best course of action.

Conclusion: Making Alt Text Work for Your Website

By following the decision tree outlined above, you can make smart choices about when and how to use the alt attribute for your images. Remember, the goal is to make your website more accessible, provide useful content for screen readers, and improve SEO.

In summary:

Use empty alt attributes for purely decorative images or when the image doesn’t add meaningful content.
Provide descriptive alt text for informative images, icons, or images with text that isn’t available elsewhere.
For complex images like graphs, include the information in the surrounding content and use the alt attribute for a brief description.

By mastering the use of alt text, you help ensure your site is accessible to all users, regardless of their abilities or limitations.