The importance of the image and the information it conveys affect how much detail the alt text requires. Some images require a more detailed description. Only describe the elements of the image that the reader must visualize to understand the content. Do not repeat information that the text already provides. Instead, determine what the image shows that the text does not already describe.

The ideal alt text description provides a visually impaired person with an experience that is equivalent to the experience of a fully sighted person. A fully sighted person views the image in context. Therefore, to provide the same information as the original image, you must explain the context and purpose of the image.

In an image that shows people and other objects in the background, ensure that the alt text you include is brief. Do not describe what each person looks like. For example, if the image shows an office environment, the alt text can simply say A busy office environment with people working.