The Importance of Alt Text for SEO and Accessibility
The alt attribute in an HTML <img> tag is one of the easiest and most impactful elements to get right, yet it's often overlooked. Writing effective "alt text" is crucial for two main reasons: it makes your website accessible to visually impaired users, and it provides valuable context to search engines, boosting your SEO.
This guide explains why alt text matters and how to write it perfectly.
What is Alt Text?
Alt text (or alternative text) is a short, written description of an image. It's added to the alt attribute of an <img> tag. Its primary purpose is to be read aloud by screen readers for users who cannot see the image.
<img src="images/golden-retriever.jpg" alt="A happy golden retriever puppy playing with a red ball in a grassy field.">It also displays on the page if the image fails to load, giving users context about the missing content.
Why Alt Text is Critical for Accessibility
For a person using a screen reader, an image without alt text is a black hole. The screen reader might announce "image" or the filename, but it provides no information about what the image contains or why it's there. Good alt text ensures that all users, regardless of visual ability, can access the full content of your page.
- It describes the content of the image (e.g., "A chart showing a 30% increase in sales").
- It describes the function of the image if it's a link (e.g., "Company logo, links to homepage").
Web accessibility is not just a best practice; it's about creating an inclusive web for everyone.
How Alt Text Boosts Your SEO
Search engines like Google are incredibly smart, but they are still text-based crawlers. They can't "see" images the way humans do. Alt text provides the crucial textual context that search engines need to understand an image's subject matter.
Benefits for SEO:
- Google Images Ranking: Well-written alt text is a major ranking factor for Google Images, which can be a significant source of traffic.
- Topical Relevance: By describing images with relevant keywords, you reinforce the overall topic of your page, which can help it rank better in regular search results.
- Image Link Context: If you use an image as a link, the alt text acts as the anchor text, providing valuable SEO signals.
Keyword Strategy: Naturally include your target keyword if it's relevant to the image, but never "stuff" keywords. Focus on being descriptive first.
How to Write Great Alt Text: The Do's and Don'ts
Writing good alt text is a skill. The goal is to be descriptive and concise.
DO: Be Specific and Descriptive
- Bad:
alt="dog" - Good:
alt="A black labrador puppy sleeping on a blue rug."
DON'T: Start with "Image of..." or "Picture of..."
Screen readers already announce that it's an image, so this is redundant.
- Bad:
alt="Picture of a laptop on a desk." - Good:
alt="A laptop on a wooden desk next to a cup of coffee."
DO: Keep it Concise
Aim for under 125 characters if possible. While there's no strict limit, screen readers often pause after this point. Be descriptive but not overly verbose.
DO: Use an Empty Alt Attribute for Decorative Images
If an image is purely decorative and adds no real content (like a background pattern or a stylistic border), use an empty alt attribute: alt="". This tells screen readers to ignore the image completely, which is better than having it read out an unhelpful filename.
<!-- This is a purely decorative separator line -->
<img src="fancy-divider.png" alt="">Conclusion
Writing alt text is a small effort that yields huge returns for both accessibility and SEO. It's a fundamental part of responsible web development.
- Every image that provides content should have descriptive alt text.
- Decorative images should have an empty alt attribute (
alt=""). - Be descriptive, concise, and never stuff keywords.
Make it a habit to write meaningful alt text for every image you add. Your users and your search rankings will thank you.
Use our Live HTML Viewer to check your site's code and ensure all your images have proper alt text!