These are the query string parameters (also called arguments) that get tagged at the end of a Youtube URL.
They are the ampersands (“&”) and text at the end of a web address (URL). In the case of Youtube, this string of of code is the query string parameters and it adds functionality to what is presented. This is a comprehensive guide of Youtube’s query string arguments.
|&hl=||hl stands for Host Language (thank you MapKi!) It is followed by “hl Parameter Values” which correspond to “Language/Locales” ex. en-US means English (United States and Canada).It also can stand for hoc loco, which is Latin for “in this place” or hl stands for “human language”, but not in this case.|
|&video_id=||Youtube video ID – used in conjunction with &get_video? to embed a Youtube video into another application. Not supported by Youtubes terms of service and may no longer work.|
|&t=||Youtube video tag – used in conjunction with Youtube video ID.|
|&fmt=||&fmt=6 is good quality, &fmt=18 is better, and &fmt=22 is the best. Video must originally be in high definition (HD) to work. May not work regardless as this feature is in beta and not available for all videos.|
|&rel=||Rel stands for related. In relation to youtube, rel=1 means show related feeds and rel=0 means don’t.|
|&fs=||Allows the fullscreen button to show up or not. 1 means it will show up, 0 means it is disabled.|
|&start=225||Starts the video 225 seconds into the video.|
|&end=230||Stops the video 230 seconds into the video.|