Glossary
Alt Text
A text description added to an image for accessibility and SEO purposes.
Definition
Alt text (alternative text) is a written description of an image added to the HTML img tag using the alt attribute. It serves two primary purposes: accessibility (screen readers read alt text aloud to visually impaired users) and SEO (search engines cannot see images but can read alt text to understand what the image depicts).
Why It Matters
Alt text is both a legal accessibility requirement in many jurisdictions and a meaningful SEO signal. Google Images can drive significant traffic — but only if images have descriptive alt text that allows them to be indexed for relevant searches.
Examples
Good alt textalt='a bar chart showing keyword density percentages for a 500-word blog post'
Bad — emptyalt='' — use only for truly decorative images
Bad — keyword-stuffedalt='keyword density keyword checker keyword tool free online best'
Common Mistakes
Leaving alt text empty for non-decorative images.
Writing alt text that starts with 'Image of...' — screen readers already announce it as an image.
Keyword-stuffing alt text.
Using the same alt text for multiple different images.