Sometimes it's inconvenient to use a movie to launch QuickTime Player. It involves another production step for one thing, and the viewer needs to have QuickTime installed just to see the movie. Starting with QuickTime 5, it's possible to launch QuickTime Player directly from a text link, which directs to a file with extension .qtl.
What is QTL?
QTL (QuickTime Link) is a file extension which is associated with QuickTime movie files on web servers, and could be downloaded or streamed.
Its format is the same as a .mov file. Indeed, you can rename .qtl files as .mov files, and it would be played in QuickTime player.
Why do we need “File Extension QTL”?
QuickTime Player supports several different kinds of reference movies-- small files, typically less than 1 Kb, that point to other movies by filename or by URL, named with file extension QTL. QuickTime plays a reference movie by getting whatever it points to and playing that.
Only the tiny reference movie is left on the user's disk, and only the reference movie has to download before the browser calls QuickTime Player. It usually takes less than a second for a small reference movie to download. The movie it points to--the real movie--can play while it downloads, so there is no need to wait to play the movie until the full movie is downloaded.
(brought to you by your friend at www.fileextensionqtl.com)