One of the most used features on my OS X installs is the Quick Look feature, its much easier then launching an app just to check, or to quickly read off its content. However, for as long as I can remember Quick Look has always been known for causing delays in folder navigation, high CPU and high network utilisation. This is generally down to it rendering previews of movie files in the active finder window. Yes – this even includes items on your desktop.
There are a couple of ways to combat this speed delay without loosing functionality of Quick Look on other files.
The easiest is to remove the Quick Look generator from the quick look folder. To do this, click on Go > Go To Folder now type or copy paste /System/Library/QuickLook/ now either delete or if you’d prefer move Movie.qlgenerator to another location.
This will disable the thumbnails for movie files, and speed up finder navigation – especially for media heavy folders.