If you use any images in your survey, they must have alt text provided for them, which describes in words what the image displays. Include only as much information as you need to convey the purpose and content of the image. If there is text in your image, you should include it in the alt text since screen readers cannot read images of text. Learn more in the WebAIM guide to alt text.
Once you edit the image’s description, you will need to remove the old version of the image from surveys it has already been added to and replace it with the new version. The new alt text will not automatically appear if the image was inserted into a survey prior to changing its description in the Graphics Library.
The second way to add alt text is to add it when you want to upload a new image in the survey builder.
After you upload your image from your computer, add your alt text into the Description field, which will be auto-populated with the filename. The description you add here will be saved in the Graphics Library and will still be associated with this image if you add it into other surveys in the future.