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.
Query |
Translation |
| &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. |
I recommend this extensive post on Youtube plugins and tools for more information and for advanced users, check out the Youtube Reference Guide.