Alt text guidelines

Do:

• Aim for about 120 characters of text or 1-2 sentences
• Be specific & accurate with your alt-text
• Be objective & neutral in your descriptions
• Consider your intended audience and what they need to understand about the image
• Be careful when marking images as decorative

Avoid:

• Starting your alt-text with “Image of” (Caveat: It’s ok to indicate what kind of image has been included, including “Screenshot of”, “Black and white image of”, “graphic of”, or “cartoon”; most screen readers say “Image:” leading into the alt-text, so starting with “Image” causes the word to be repeated)
• Including every detail in the image
• Confusing images captions with alt-text
• Using inaccurate or subjective alt-text to describe an image
• Including every detail in the image
• Relying on auto-generated alt-text

Alt-text v captions

Alt-text:

• Describes what’s in the image
• Uses description to paint a clear picture of the image
• Does not need to include all image details
• Cannot typically be read on the page

Captions:

• Identify what the image is about: citation information
• Snippets of context
• Can be read on the page

(based on TTaDA’s “Simple Images”)