What Makes a Good Alt Tag Text?

Characteristics of Effective Alt Text

• Be Specific and Descriptive. Good alt text should accurately describe what appears in the image with enough detail to replace the visual information. Generic descriptions like "image" or "photo" don't provide value to users who cannot see the image.
• Consider Context. The ideal alt text varies depending on the image's purpose and surrounding content. An image's meaning might change based on where and how it's used on your website.
• Keep It Concise. While descriptive, alt text should remain concise. Most screen readers work best with alt text under 125 characters. Prioritize the most important information about the image.

"Alt text serves as the voice of your images for those who cannot see them. It's not just about accessibility compliance—it's about creating an inclusive web experience for everyone."

Good alt text should avoid keyword stuffing. While alt text is important for SEO, stuffing it with keywords creates a poor experience for screen reader users and may trigger search engine penalties. Instead, use natural language that accurately describes the image's content while incorporating relevant keywords where they make sense.

Best Practices for Alt Text

When writing alt text, omit phrases like "Image of" or "Picture of." Screen readers already announce that an element is an image, so including these phrases is redundant and wastes valuable character space. Focus instead on describing the content and meaning of the image.

Include any text that appears within images in your alt attribute. If your image contains text that conveys important information, such as an infographic with statistics or a button with action text, this content must be included in your alt text to maintain accessibility.

Special Considerations for Different Image Types

For product images, focus on key features, colors, and uses that would help someone make a purchasing decision. A good example would be: alt="Stainless steel programmable coffee maker with 12-cup carafe and built-in grinder".

When adding alt text to charts and graphs, summarize the data trend or main conclusion, not every data point. For instance: alt="Graph showing steady increase in sales from January to June 2023 with 45% overall growth".

Using Empty Alt Text Appropriately

Not all images require alt text. Decorative images that don't add informational content should use empty alt attributes (alt="") to be ignored by screen readers. This applies to images used for aesthetic purposes only, such as decorative borders, spacers, or background textures.

Alt Text and SEO Benefits

While accessibility should be your primary motivation for using alt text, proper implementation also benefits your SEO efforts. Include target keywords naturally when relevant to the image content and use descriptive filenames that reinforce the alt text (e.g., "golden-retriever-puppy.jpg" instead of "IMG00023.JPG").

Ensure image relevance to the surrounding content and page topic, and add structured data where appropriate to help search engines better understand your images. Maintain consistency between image captions and alt text while avoiding duplication.

Testing Your Alt Text Effectiveness

To ensure your alt text is serving its purpose, try using a screen reader to experience how your content is read aloud. Turn off images in your browser to see if the alt text effectively replaces the visual content and use accessibility testing tools like WAVE, axe, or Lighthouse to audit your website.

Automating Alt Text with Alttagger

Modern AI technology, like that used by Alttagger, can help generate high-quality alt text automatically by recognizing objects, people, and actions in images, understanding the context of where images appear, and creating natural language descriptions that balance detail with conciseness.

Alttagger scales alt text creation across thousands of images, making it an efficient solution for websites with extensive image libraries. However, while AI can dramatically improve efficiency, human review remains important for ensuring accuracy and contextual relevance.

Conclusion

Creating effective alt text is both an art and a science. By focusing on descriptive, contextual, and concise attributes, you can make your website more accessible while improving your SEO performance. Remember that good alt text serves real people first and search engines second.

By implementing the practices outlined in this guide, you'll create a more inclusive website experience for all users while simultaneously improving your visibility in search results—a true win-win approach to web content.