Alt Text
Also known as: Alternative Text, Alt Attribute, Alt Tag
The alternative text attribute on an image element that describes the image in words. Screen readers announce it to visually impaired users, and it displays when an image fails to load. Search engines read it to understand image content, making it essential for both accessibility and image search visibility.
Key Takeaways
- Alt text is the alternative text attribute on an image element that describes the image in words.
- Screen readers announce alt text to visually impaired users, making it a core accessibility feature.
- It also displays in place of an image when the image fails to load.
- Search engines read alt text to understand image content, which supports image search visibility.
- Decorative images should use an empty alt attribute so screen readers can skip them.
How It Works
Alt text lives in the alt attribute of an image tag. When a screen reader reaches the image, it reads the alt text aloud, letting a visually impaired user understand what the image conveys. If the image file cannot load, the browser shows the alt text in its place, so meaning survives a broken connection.
Search engines cannot see pixels, so they rely on alt text, surrounding copy, and the file name to interpret an image. Good alt text describes the image's content and function plainly, which reinforces the page's topical relevance much like a well-written Title Tag or Meta Description signals a page's subject.
For images that carry data or meaning beyond a caption, pairing descriptive alt text with Structured Data helps engines index the image accurately. Decorative images that add no information should use an empty alt attribute so assistive tech skips them rather than announcing clutter.
Why It Matters
Alt text is the primary way search engines interpret images, so it drives image search traffic and reinforces a page's topical relevance. It is also a legal accessibility requirement under standards like WCAG.
Example
An ecommerce store sells a hiking backpack. Instead of alt text reading "image" or "backpack backpack hiking bag," the product photo uses "Green 40-liter hiking backpack with side water bottle pockets." A screen reader user hears an accurate description, the text appears if the image fails, and image search can match the photo to relevant queries.
Common Mistake
Keyword-stuffing alt text, describing decorative images that should have empty alt attributes, or omitting it entirely. Writing 'image of logo' adds no value; describe function and content instead.
Frequently Asked Questions
What is good alt text?
Good alt text concisely describes the image's content and function in plain language, around a sentence or less. It avoids phrases like "image of," avoids keyword stuffing, and conveys what a sighted user would gain from seeing it.
Do decorative images need alt text?
No. Purely decorative images should use an empty alt attribute (alt="") so screen readers skip them. Adding descriptions to decorative images creates noise for assistive technology users without providing any useful information.
Does alt text help SEO?
Yes, indirectly. It helps search engines understand image content, supporting image search visibility and reinforcing page relevance. It should be written for accuracy and accessibility first, not stuffed with keywords, which can look manipulative.