As new accessibility laws are in effect, meeting web accessibility requirements are becoming more challenging. Closed Captions (CC) help individuals with deaf or hard of hearing view videos and make it more accessible as captioning describes dialogue and audio cues such as music or sound effects. It is helpful even for persons with normal hearing when the audio cannot be heard due to noise (restaurants, public spaces, etc.) or in quiet locations such as hospitals or a libraries.
Software from CPC allows you to create closed captions for the most popular web formats such as HTML5, YouTube, Flash, QuickTime, iTunes, and Windows Media, as well as convert existing closed captions into web formats. For example, MacCaption is the only software that enables the HD closed captioning functions of Final Cut Pro 7. You can modify and output both HD and SD closed captions to tape, file, disc, mobile devices, and the web. It works for both Windows and Mac. So if you often create videos and film, consider adding captioning to be accessible for all audience (CRC MacCaption).
If you do not have the software, but you want to add captioning on a YouTube video you created, check out this video by BigNate84 (BigNate84 Howto). You do not need the CPC software for this purpose. How To Add Closed Captions To A YouTube Video