Closed-captions are available for any video that has been originally captioned by the service that the video has been pulled from.
Enabling closed captions
When a user watches a video-lesson from a video which has closed-captions added, a “CC” button will appear. Click the button to enable/disable the subtitles:
Enabling different languages
There also may be videos subtitled in different languages. To go through the options, click the “CC” button again:
No captions available
If the video does not have subtitles available, the "CC" button will not appear at the bottom of the video, as in this case:
Please note that while some videos may contain subtitles on YouTube, many actually use a speech recognition technology to automatically generate subtitles on the fly. This feature unfortunately doesn't work on other sites -- like ours.