What is image alt text and when should it be used?

Alternate text, also called alt tags and alt descriptions, describes images to visually impaired users. Without alternative text, the content of an image will not be available to screen reader users. Each image that conveys meaning or is used as link content must include alternate text unless including the alternate text would create redundancy (e.g. when text is also included in an image caption or text inside the body of a link). Images used strictly for decoration should not include alt text.

Additional Resources:

• WebAim – Alternate Text
• W3.org – Using alt attributes on img elements