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Describing Images

We all know that adding ALT text to our images is a very simple way to help add accessibility to our websites and digital assets.

But there are other forms of text alternatives that, when used properly, also make your digital creations accessible.

One of those alternatives is called Long Description. Not to be confused with the HTML longdesc attribute (which, by the way, has been deprecated and is not supported by any modern browser). A long description is an extended version of an ALT text used to describe complex images. Complex images are images such as:

  • "graphs and charts, including flow charts and organizational charts;
  • diagrams and illustrations where the page text relies on the user being able to understand the image;
  • maps showing locations or other information, such as weather systems."

~ Complex Images, W3C WAI

Like good ALT text, long descriptions should be clear, concise, and as descriptive as possible. Most importantly, long descriptions include vital information about the image. For example, a floor plan. The long description would include directional language to point out where the kitchen is located in relation to the front door. Is the bathroom on the right-hand side of the hallway or the left side? How many square feet is the living room?

"Long descriptions should be formatted using headings, etc., just as with other content." ~ What is Long Description?, Colorado State University

The W3C suggests making the image description part of the main content in some cases to help reach a wider audience.

Another form of alternative text is image captions. Image captions are available to ALL users, as they are displayed directly beneath the image. The difference is that captions do not fully describe the image but merely provide additional information. Captions should never be used as a substitute for ALT text or long descriptions. But a well-written caption does give the user valuable supplemental context to the image.

National Public Radio, NPR, has very specific guidelines for captioning images.

And what about the HTML title attribute? Can that be used as an alternative text? According to The A11Y Project: "Short answer: Don't use them, except in special circumstances." And those "special circumstances" are:

  • "For <frame> and <iframe> elements.
  • For providing a label when a text label would be redundant.
  • If you must use title on images, keep it the same as the alt."

The W3C offers some really great Tips and Tricks for writing your best alternative text and provides an ALT Decision Tree that can help you decide when and what type of alternative text is needed for every situation.


Maggie Vaughan, CPACC
Content Marketing Practitioner