The Complete Guide to Alternative Text (ALT) for Web Accessibility & SEO

As the internet becomes an increasingly vital part of our daily lives, it‘s more important than ever to ensure that web content is accessible to everyone – regardless of ability. One of the key ways to make the web more inclusive is through the proper use of Alternative Text, commonly known as ALT text.

In this comprehensive guide, we‘ll dive deep into everything you need to know about ALT text, from the basics of what it is and why it matters, to advanced techniques for crafting effective descriptions. Whether you‘re a web developer, content creator, marketer, or just someone who cares about digital accessibility, understanding ALT text is essential. Let‘s get started!

What is ALT Text?

Put simply, ALT text is a written description of an image that gets read aloud by screen reader software used by visually impaired individuals. It‘s like an invisible caption that conveys the meaning and context of graphics to those who can‘t see them. The ALT attribute is added to the HTML tag to provide this text-based alternative.

Here‘s an example of what ALT text looks like in code:

ALT text was first introduced in HTML 2.0 in 1995 to make the rapidly growing world wide web more accessible. According to the World Wide Web Consortium (W3C), providing a text alternative for non-text content is the very first item on their checklist for web accessibility.

The Web Content Accessibility Guidelines (WCAG) state that "All non-text content that is presented to the user has a text alternative that serves the equivalent purpose." This encompasses more than just images – it also applies to icons, buttons, charts, embedded media, and other visual elements.

Why ALT Text Matters

For the 2.2 billion people worldwide who have a vision impairment, ALT text can make or break their online experience. Without these descriptions, visually impaired users relying on assistive technologies would miss out on critical information and context.

Imagine reading a news article discussing the latest developments in space exploration. Amazing photographs from the Hubble telescope are a key part of the story – but if those images aren‘t properly tagged with ALT text, it‘s like they don‘t exist for screen reader users. They‘re left with gaping holes in their understanding.

But even for sighted users, ALT text proves invaluable in certain situations:

• When images fail to load due to a poor connection
• For users who turn off images to conserve cellular data
• When browsing the web using a text-only browser or screen

Beyond accessibility, ALT text also carries significant benefits for search engine optimization (SEO). Since search engine bots can‘t "see" images the same way humans do, they rely on ALT text to understand and index the content of graphics. This helps search engines determine the relevancy of an image to a user‘s query.

As Moz explains, "ALT text provides search engines with useful information about the subject matter of the image. It‘s an opportunity to include your target keyword. And it‘s believed that keywords in ALT text have a stronger impact than keywords in the surrounding text.

Well-optimized images with descriptive ALT text can boost your search rankings, drive traffic, and help your content get discovered by a wider audience. On the flip side, neglecting ALT text represents a lost opportunity to connect with searchers and may even hurt your SEO.

Crafting Effective ALT Text

Now that we understand the importance of ALT text, let‘s explore some best practices for writing it effectively. The key is to provide a concise yet meaningful description that captures the purpose of the image and considers the surrounding context.

Some general guidelines:

• Keep it brief, ideally under 125 characters. Screen readers tend to cut off longer descriptions.
• Be specific and descriptive, but avoid redundancy. Don‘t repeat information already present in captions or body text.
• If the image contains text, include that text verbatim in your description.
• For decorative images that don‘t add meaning, use an empty ALT attribute (alt="").
• Avoid phrases like "image of" or "photo of" since screen readers already identify images.
• End your description with a period to indicate a pause for screen readers.

Let‘s look at a few examples to illustrate good vs bad ALT text:

Good:

Bad:
(Not descriptive enough)

Good:

Bad:
(Doesn‘t convey data insights)

For complex images like infographics or diagrams, a short ALT description may not suffice. In those cases, it‘s best to provide a more detailed explanation in the surrounding text or link to a separate page with a long description.

Implementing ALT Text

Adding ALT text to your images is a straightforward process. In HTML, simply include the alt attribute within the tag:

Most content management systems (CMS) like WordPress also provide fields for entering ALT text when uploading images through the media library or page editor.

It‘s important to note that ALT text should be determined by the function and context of the image, not just a literal description of its contents. As WebAIM puts it, "Alternative text should present the content and function, not necessarily a description, of an image."

For example, the ALT text for a search button icon should be something like "search" rather than "magnifying glass." The former describes the button‘s function while the latter only describes its appearance.

When used in conjunction with other accessibility best practices like proper heading structure, keyboard navigation, and sufficient color contrast, ALT text helps create an inclusive user experience for all.

Evaluating & Testing ALT Text

To ensure your ALT text is effective and WCAG compliant, it‘s important to test it regularly. Some helpful evaluation tools and techniques:

• Use a screen reader like NVDA or VoiceOver to hear your descriptions read aloud. Does the meaning come across?
• Run automated accessibility scans with browser extensions or online tools to check for missing ALT attributes.
• Manually review a sample of pages to assess ALT text quality and consistency.
• Conduct user testing with people who have vision impairments to get direct feedback.
• Check Google Image Search results to see if your images are indexed with the right keywords.

Making ALT text assessment a part of your routine web maintenance process helps catch issues early and holds your team accountable to accessibility.

The Future of ALT Text & Web Accessibility

As artificial intelligence continues to advance, we may see more sophisticated approaches to auto-generating ALT text. For example, some image recognition algorithms can now analyze a photograph and provide a surprisingly accurate description. However, an automated ALT text is not a complete substitute for a thoughtful, human-written description.

Looking ahead, a growing focus on web accessibility will make ALT text even more essential. With legislations like the Americans with Disabilities Act (ADA) and Web Accessibility Initiative – Accessible Rich Internet Applications (WAI-ARIA) setting higher standards for digital inclusion, ALT text isn‘t just a "nice to have" anymore. It‘s becoming a legal and ethical imperative.

As World Wide Web inventor Tim Berners-Lee famously said, "The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect." By embracing ALT text and other accessibility pillars, we can help make his vision a reality for all internet citizens. The work starts now – and it starts with you.