Images not only provide visual appeal to our pages, but they also convey important information. The old adage, that a picture tells a thousand words, can be very true! The problem occurs when we add an image that provides the content to our students, but fail to provide an adequate text alternative for students who are visually impaired. The alternative text – called alt text for short – feature allows you to provide a description of the image.
There are times when images not only provide information but also serve a function, such as a button or links to additional resources. In this case, the alt text should communicate the function.
There are scenarios where descriptive alt text is not required and the use of the image is intended as visual decoration only. In this case, alt text is not necessary as the image has no real content value. Many images, however, have a pedagogical purpose, and , therefore , require descriptions explaining the information the images conveys.
General rules for alt text
When thinking of an appropriate text description, the alt text should be:
- Accurate: including spelling, grammar, and proper punctuation.
- Concise: using the fewest words possible while providing a meaningful description for the image.
- Equivalent: presenting the same content and/or function of the image.
Ask yourself when writing an alt text, “If you have to describe it over the phone, what would you have said?”
- Stating “image of”, “graphic of”, or “picture of” in the alt text field. Assistive technologies will announce if the object is an image, so including this information is redundant and not necessary. If the image medium is an important aspect (such as a photograph or oil painting), then the medium should be included.
- Adding the file extension, such as .jpg or .png, to the alt text description.
Writing effective alt text practice
Based on the guidance above, take a moment to think of an alt text for the image below:
You may have written, “Alice at the Mad Tea Party with the Hare, Dormouse, and Mad Hatter”. Now, how would the alt text change if this was an art class focused on the illustration style?
The alt text will depend on the context and intention of the image.
A descriptive alt text may be, “John Tenniel’s cross-hatching illustration style is a linear drawing technique that uses lines to create shadows.”