Facebook and Twitter Improving Accessibility for the Visually Impaired Is Noble, But Both May Have Another Motive Both social network giants have introduced tools that allow users to hear details about photos.

Facebook on Monday joined Twitter in making its site more accessible to the visually impaired. Not only does this boost the number of potential users for both sites, it also puts them ahead of a potential government mandate.

"There is not really a financial risk for the companies not to do these things," Andrew Johnson, a managing vice president at Gartner, told Entrepreneur. "There is an outside chance that the Department of Justice could have what they call a demand letter against them if there is a petition that their website or application is not accessible. It's fairly rare, but a very effective motivation tool."

Facebook on Monday rolled out a tool called automatic alternative text, which allows people who are blind or visually impaired using a screen reader on an iOS device to be able hear more in depth descriptions of the images that pop up in their feeds.

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Twitter last week announced its own alternative text feature for images. By selecting the "choose image description" option in the accessibility settings for the app, users will be able to include up to 420 characters for the photo's description.

More than 2 billion images are shared on Facebook, Instagram, Messenger and WhatsApp. There are more than 20 million Americans living with vision loss.

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"I think what we're seeing from Facebook today and Twitter last week, is them just doing the right thing and getting around to it," Johnson says. "I would say both took way too long to do it -- but better late than never."

Previously, Facebook users would hear only their friend's name and that he or she was in a photo, but with automatic alternative text, they'll hear how many people are in the picture, how many comments and likes there currently are, and the words "image may contain" followed by elements of the photo such as jewelry, smiling, outdoor, cloud or foliage.

Related: This Brilliant Braille Smartwatch Lets the Visually Impaired Feel What Time It Is

The development of the technology was informed in part by a paper that Facebook worked on with Cornell University to better understand how visually impaired users interact with social media.

While the technology is currently only available in English for iOS users in the U.S., U.K., Australia, Canada and New Zealand, the company says that it is working on expanding into more countries and languages.