What is an Image Description?

 

An image description is a textual description of visual content designed to improve accessibility and discoverability. An image description provides context and function and helps tell the story of digital content to readers.

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What Form Do Image Descriptions Take?

 

Image descriptions are also known as Alt-Text (or Alternative Text).

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An HTML Alt Attribute is used to assign an image description to an image, as shown in the example below. The image source (filename) is named and the image is described:

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<img src=“Cat.jpg” alt=“A cat sits on a mat.”>

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For more complex images, a longer description may be used to provide extra detail for the user. This long or extended description is either placed on another page and linked to from the original image or is included as a expandable section on the page.

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How do Image Descriptions Work?

 

ACCESSIBILITY

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Screen reader technology allows image descriptions to be accessed by users. A screen reader is a software application that converts the text into speech or touch (for Braille readers). Image descriptions are essential as they provide the user with the context and function of the image.

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DISCOVERABILITY

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Image descriptions convey semantic meaning which can be understood by search engine technology. The search engine compares the textual web search query to the textual data stored in the image description and returns a result for matching criteria. The more descriptive and contextual the image description is, the higher the image is placed in search results.

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Why are Image Descriptions Important?

 

ACCESSIBILITY

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Modern-day media content is filled with images that tell a story. Without descriptions, this information is not accessible to blind, low-vision and dyslexic readers who need an audio version.

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WebAIM states that “Adding alternative text for images is the first principle of web accessibility.”

 

DISCOVERABILITY

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Website content is evaluated and ranked based on complex algorithms and image descriptions play an integral role. Website content will not be discovered by search engines if it is not structured and labeled correctly. A WebAIM study of 1 million website homepages found that 57% of images did not include appropriate image descriptions. This has a significant impact on content discoverability.

 

Does Every Image Need a Description?

 

Every image needs to have a completed Alt Attribute. However, this does not mean that every image requires an image description. If an image is decorative and its contents are not important to user understanding, then an empty Alt Attribute (alt=“”) tells the screen reader that the image is decorative and can be skipped over. This helps the user to focus on the most relevant content.