Probably the most common accessibility error found on websites and digital documents is the absence of an Alternative Description for images and other “objects.” The Alternative Description – sometimes called the “ALT tag” – is a piece of meta code that provides information about the image so that people with low vision, who use a screen reader technology, will know what the image is.
When a screen reader user encounters a graphic file on a webpage, or in a digital document – like a PDF – the screen reader software announces the presence of the image. Without the ALT tag, the user knows the image is there, but NOT what it is an image of.
In many cases – I’ll estimate 90% of the time – images on websites or in documents are simply “pretty pictures” that decorate or provide some affective element to the document. But in some cases, the image may be used to communicate information. For example, on many webpages, the developer may include the icon for a link to their social media account. There may be a image of the Facebook logo which links to the owner’s Facebook page. When the screen reader comes across this image, their software announces there is an “image” and a “link” but does not tell them what the image communicates or where the link leads unless there is an ALT tag.
Over the past few years, the number of “tweets” that contain images has skyrocketed. Now that everyone has a camera in their cell phone, it is very easy to pop an image onto Twitter. But until today, there was no way to add an ALT tag to images in Twitter. BTW, accessibility experts and people with disabilities have been asking for this since the day Twitter started.
Now if Facebook would only follow suit…