Understanding Alt Text: A Comprehensive Guide

In the world of web development and digital accessibility, alt text, or "alternative text," plays a critical role in both user experience and search engine optimisation (SEO). It serves as the text-based description of images embedded in a webpage, helping ensure that all users, regardless of their abilities or device limitations, can access and understand the content. Whether you're a web developer, digital marketer, or someone new to accessibility, understanding how to use alt text properly is essential for creating inclusive, SEO-friendly websites.

The Importance of Alt Text

Alt text is more than just a technical requirement; it’s a bridge to accessibility and online visibility. For users with visual impairments, alt text enables screen readers to describe what an image contains, allowing those users to participate fully in the digital space. Beyond accessibility, alt text also contributes to SEO by helping search engines better understand what an image represents, thus improving a website's search rankings.

By ensuring your images are tagged with relevant and meaningful alt text, you're not only providing a better user experience but also boosting your website’s discoverability. This combination of benefits underscores why alt text has become an indispensable part of modern web design.

How Alt Text Works in HTML

Alt text is implemented within the HTML of a webpage, using the alt attribute inside the <img> tag. It looks something like this:

‍

<img src="image.jpg" alt="A woman holding a red umbrella during a rainy day.">

‍

In this example, the alt text provides a clear and concise description of the image, allowing screen readers to convey the visual content to users who cannot see the image. If for some reason the image fails to load, this text will be displayed in its place, ensuring that no content is lost.

Alt Text and Accessibility

For users with disabilities, particularly those with visual impairments, alt text is a vital tool. When someone visits a website using a screen reader, the software reads out the alt text for images, making it possible for them to "visualise" the image through a detailed description. Without it, they would miss out on key content, whether it's an important infographic, a product image, or a photo that adds context to an article.

Alt text also helps users with cognitive disabilities who may rely on simplified, structured content to understand what’s on the page. Providing accurate and meaningful alt text ensures that no one is left out of the digital experience.

Alt Text and SEO

From an SEO perspective, search engines like Google rely on alt text to understand the contents of an image. Since search engine crawlers cannot "see" images the way humans do, alt text allows them to index and rank images correctly. This is particularly important for image searches, where having optimised alt text can significantly improve a website’s visibility.

For example, if you run an online store that sells "red running shoes," adding the appropriate alt text to your product images (e.g., "A pair of red running shoes on a white background") will help those images appear in relevant search queries, increasing your chances of attracting organic traffic.

Best Practices for Writing Alt Text

Crafting effective alt text requires more than just describing an image. It’s about providing enough context so that users and search engines can understand the image's relevance without overloading them with unnecessary information. Here are some best practices to follow:

• Be Descriptive but Concise: Aim to describe the image in a way that conveys its meaning without being overly verbose. For example, "A golden retriever playing fetch in a grassy field" is more effective than just "dog" or "golden retriever."
• Avoid Keyword Stuffing: While it’s important to include relevant keywords, avoid overloading the alt text with them. This can harm both user experience and SEO rankings. Use keywords naturally, only where they make sense.
• Focus on Functionality and Context: Consider the purpose of the image. If it’s decorative, you may not need alt text at all (more on that later). But if the image conveys essential information, ensure the alt text reflects its role within the content.
• Keep It Under 125 Characters: Screen readers typically cut off alt text after 125 characters, so it’s best to stay within this limit to ensure the full description is conveyed.

Common Mistakes with Alt Text

Many websites overlook or misuse alt text, which can lead to poor user experience and missed SEO opportunities. Here are some common mistakes and how to avoid them:

• Empty Alt Text for Important Images: Forgetting to add alt text for key images like product photos or infographics can leave users in the dark.
• Using “Image of” or “Picture of” in the Alt Text: Screen readers already know they’re reading an image, so phrases like “image of” or “picture of” are redundant. Get straight to the description.
• Alt Text for Decorative Images: If an image is purely decorative and doesn’t add context to the content, leave the alt attribute empty (alt=""). This signals to screen readers to skip the image.

How to Write Descriptive Alt Text

When writing alt text, focus on accurately describing the content and function of the image. Here are a few tips:

• Use Specific Descriptions: Instead of general terms, be specific about what’s in the image. For example, "A black cat sitting on a window sill watching the rain" is more descriptive than "cat by window."
• Consider Context: How does the image relate to the content around it? If it’s part of an article about rainy weather, include that context in the alt text.
• Avoid Fluff: Get straight to the point. Long-winded alt text can confuse screen reader users and dilute the content’s meaning.

When to Use Alt Text and When Not To

Not every image on your site needs alt text. For example, purely decorative images, such as background patterns or spacer images, should have an empty alt attribute (alt=""). This prevents screen readers from wasting time on visuals that don’t contribute to the overall message.

On the other hand, images that convey information, such as charts, graphs, infographics, and product images, should always have descriptive alt text. If you’re unsure whether to include alt text, ask yourself: does the image add meaning or context to the page? If the answer is yes, then alt text is necessary.

Writing Alt Text for Complex Images

Some images are more complex, such as charts, infographics, or maps. In these cases, writing effective alt text can be tricky because there’s often a lot of information to convey. Here’s how to handle it:

• Summarise Key Points: For a complex infographic, focus on the main takeaway rather than every detail. For instance, "An infographic showing the rise in smartphone usage from 2010 to 2020" might be enough to describe the image.
• Use Captions: Sometimes, the alt text cannot fully capture the details of an image. In such cases, a detailed caption or nearby explanation can complement the alt text to provide users with a fuller understanding.

Examples of Good and Bad Alt Text

Here are a few examples to illustrate effective alt-text writing:

• Good Example: For an image of a dog fetching a ball: “A golden retriever running on the beach with a tennis ball in its mouth.”
• Bad Example: “Dog playing.” This lacks detail and doesn’t provide enough context to be meaningful.

For decorative images, here’s how it should look:

• Empty Alt Attribute: <img src="decorative-pattern.jpg" alt=""> – This tells screen readers to skip over the image, as it provides no additional content.

Alt Text for Different Types of Media

Alt text isn’t just for photos. It can also be used for:

• Logos: Describe the logo briefly, like “Company X logo.” If the logo is linked to the homepage, the alt text can be “Company X homepage.”
• Videos: While alt text itself isn’t used for videos, ensure that video content includes captions or transcripts for accessibility purposes.
• Icons and Buttons: For interactive elements, ensure the alt text or ARIA labels describe their functionality (e.g., “Search button” or “Download icon”).

How to Test the Effectiveness of Alt Text

Testing your alt text for functionality and clarity is essential. You can:

• Use Screen Readers: Tools like VoiceOver (on macOS) or NVDA (on Windows) can help you experience your website the way a visually impaired user would.
• Run Accessibility Audits: Tools like WAVE or Google Lighthouse can scan your site for missing or poorly written alt text.

Alt Text for E-commerce and Product Images

In the world of e-commerce, product images play a critical role in sales. Well-written alt text for product photos can enhance the shopping experience for users with disabilities and improve your site's visibility in image search results. When adding alt text to product images, describe the product’s key features. For example:

• "Men's blue running shoes with white soles" is far more informative than just "blue shoes."

Alt Text for Social Media Platforms

Social media platforms like Facebook, Instagram, and Twitter now support alt text for images. On these platforms, the same principles apply: provide descriptive, relevant alt text that explains what’s in the image. For instance, when sharing a photo of a product on Instagram, include an alt text that captures the essence of the image, such as "A hand holding a cup of coffee next to an open notebook."

Tools and Plugins for Generating Alt Text

If you manage a large website with hundreds or thousands of images, manually adding alt text can be overwhelming. Fortunately, there are tools and plugins that can help streamline the process:

• Automatic Alt Text Generators: Some CMS platforms offer AI-powered alt text generators that scan your images and suggest relevant descriptions. While useful, these tools should always be reviewed by a human for accuracy.
• SEO Plugins: Tools like Yoast SEO for WordPress can remind you to add alt text and even suggest improvements based on SEO best practices.

Alt Text in Modern Web Design

As web design continues to evolve, the importance of alt text remains constant. Designers must integrate accessibility into their workflow from the beginning, ensuring that alt text complements the visual aesthetics and functionality of the site. The push towards more inclusive digital experiences means alt text will remain a key consideration in all future web projects.

Frequently Asked Questions (FAQs)

1. Why is alt text important for accessibility?
‍

Alt text provides descriptions of images for users who rely on screen readers, helping them access the same visual content as sighted users.

‍

2. How does alt text improve SEO?
‍

Search engines use alt text to understand what images represent, improving your site's ranking in image search results and overall visibility.

‍

3. Should I add alt text to every image on my site?
‍

No, alt text is only necessary for informative images. Decorative images can be marked with an empty alt attribute (alt="").

‍

4. How long should alt text be?
‍

Aim for fewer than 125 characters to ensure screen readers can deliver the full description without cutting off the text.

‍

5. Can I use alt text for social media images?
‍

Yes, many social platforms support alt text for images, allowing you to provide accessible content across various channels.

‍

6. Are there tools to help automate the creation of alt text?
‍

Yes, tools like automatic alt text generators or SEO plugins can assist with generating alt text, though it’s best to review their suggestions manually.