Video has played an important role in education for many decades. Now, in the form of computer-based multimedia, video is increasingly utilized in distance learning and other web-based educational applications. However, the audio portion of a video presentation is inaccessible to people who are deaf or hard of hearing unless it includes captions. Captions are on-screen text descriptions that display a video product's dialogue, identify speakers, and describe other relevant sounds that are otherwise inaccessible to people who are deaf or hard of hearing. Captions are synchronized with the video image so that viewers have equivalent access to the content that is originally presented in sound, regardless of whether they receive that content via audio or text. Captions are either open or closed. Open captions always are in view and cannot be turned off, whereas closed captions can be turned on and off by the viewer.
For video that is displayed on television sets, special devices called decoders must be available in order to view closed captions. Since 1993, decoders have been required to be built into television sets 13 inches or larger sold for use in the United States.
When videos are accessed on the World Wide Web, they also may have captions that are open or closed. Closed captions appear only when the user agent (e.g., a media viewer player) supports them. At least one version of most major media viewer software applications now supports closed captions. Some of these products may support captions in their stand-alone client versions but not in browser-embedded or handheld versions of their products.
Delivering video products with closed captions places responsibility on the user to understand how to turn captions on, either on their television sets or in their media viewer software. So that the user isn't faced with this burden, some people argue in favor of delivering video products with open captions. Open-captioning proponents also argue that captioning has universal design  benefits for people other than those with hearing impairments (e.g., people whose first language is not English; people in noisy airports, health clubs, sports bars). Also, when the spoken word of all speakers is open-captioned, additional translation for speakers who have speech impairments is not required.
Despite the advantages of open captions, there also are disadvantages. Some disadvantages stem from the fact that open captions are an actual part of the video stream, whereas closed captions exist as a separate text stream. If captions are preserved as text, users potentially can archive and index video content and allow users to search for specific video content within these archives; this ability is lost with open captions. Also, open captions, unlike closed captions, are subject to loss of quality when the encoded video is compressed.
With the mix of advantages and disadvantages of open and closed captioning, it is important for the video producer to evaluate the use of the video product and make an informed decision about what type of captioning to use. For example, if a training videotape is specifically designed for individuals with disabilities or for large audiences or for use in noisy conference exhibits, open captioning might be a good choice. The most important decision is to choose to caption the product; the choice to make it open-captioned or closed-captioned should occur after consideration of all factors regarding its use.
-  universal design