Functional Images
Functional images add value to the content because they provide more information than can be provided through text alone.
Altenative Text
Alternative text (or alt text) is text that describes a functional image. It makes it possible for people using assistive technologies to access the information conveyed by an image. It also helps search engines better understand the purpose of the image.
Include long descriptions for complex images
Long descriptions explain information that is presented in complex infographics or images. You must provide a long description if you can't describe the content and function of the image in less than 140 characters. If you can describe the image in less than 140 characters, use alternative text instead. If a detailed and equivalent explanation of the image appears in the text immediately before or after a complex image, you don't have to provide a long description.
Decorative Images
Images that are for decorative purposes only don’t require alt text.
Here’s when we consider an image decorative:
- The image doesn’t provide important context to the page content
- The image isn’t used as a link to direct people to more information
Alt Text
When you're writing alternative text for a functional image:
- Describe the image as if you were describing it to someone over the phone
- Limit the text to around 140 characters (including spaces)
- Use the text that is embedded in the image only if it provides enough context; otherwise, write different text that includes more information
- Don't use "image of..." or "graphic of..." to describe the image; screen readers do this already