What is Alternative Text (Alt Text)?
Alternative text, commonly known as alt text, is a short, descriptive text that explains the content and function of an image within its context. This HTML attribute serves as a text replacement for images when they cannot be displayed or accessed visually. Alt text is essential for web accessibility as it allows screen readers to convey visual information to blind and low-vision users, ensuring digital inclusion for all website visitors.
For example, instead of a screen reader simply announcing "image," proper alt text like "Red stop sign at intersection" provides meaningful context about the visual content.
Importance in Web Accessibility
Alt text is a fundamental requirement for accessibility compliance under major standards and regulations:
- WCAG (Web Content Accessibility Guidelines): Success Criterion 1.1.1 requires that all non-text content has appropriate text alternatives
- ADA (Americans with Disabilities Act): Courts increasingly reference WCAG standards in ADA compliance cases
- BFSG (Barrierefreiheitsstärkungsgesetz): Germany's accessibility law mandates accessible digital services
Proper alt text implementation helps organizations meet legal requirements while creating inclusive digital experiences that serve users with visual impairments, cognitive disabilities, or those using assistive technologies.
Implementation and Best Practices
Alt text implementation varies across platforms but follows consistent principles:
HTML Implementation
<img src="chart.png" alt="Sales increased 25% from January to March 2024">
CMS Platforms
- WordPress: Add alt text in the media library or block editor's image settings
- Drupal: Include alt text when uploading images or editing image fields
- Shopify: Edit alt text in product image settings or theme customization
Writing Effective Alt Text
- Be concise but descriptive (aim for 125 characters or less)
- Describe the image's purpose and context, not just appearance
- Include relevant text that appears in images
- Avoid redundant phrases like "image of" or "picture of"
- For decorative images, use empty alt text (alt="") to indicate they should be ignored by screen readers
Common Mistakes and Misconceptions
Several misconceptions can undermine alt text effectiveness:
- Misconception: Alt text is just for blind users
Reality: It benefits users with slow internet connections, cognitive disabilities, and helps with SEO - Mistake: Using filename as alt text (e.g., "IMG_1234.jpg")
Solution: Describe the image's content and context instead - Mistake: Writing overly long descriptions
Solution: Use concise, relevant descriptions; consider longdesc for complex images - Mistake: Adding alt text to decorative images
Solution: Use empty alt text (alt="") for purely decorative elements - Technical Note: While often called "alt tags," they are actually HTML attributes, not tags
Advanced Considerations
For complex images like charts, graphs, or infographics, consider:
- Using brief alt text with detailed descriptions in surrounding content
- Implementing the longdesc attribute for extensive descriptions
- Providing data tables as alternatives to chart images
- Using ARIA labels for enhanced accessibility context
Key Takeaway
Effective alt text is crucial for web accessibility and WCAG compliance. Focus on writing concise, contextually relevant descriptions that convey both the content and function of images. Remember that good alt text benefits all users, not just those using assistive technologies, while helping organizations meet accessibility standards and create truly inclusive digital experiences.