Unity ads folder being created

Why is that when I launch my app I see that a folder called “UnityAdsVideoCache” is created with a test video inside it.I’m using unity 5.2. For ads I’m using chartboost and admob but not unity ads.

It’s presumably something automatic unity does, since unity ads are integrated into unity 5.2+. It shouldn’t effect your builds or performance since it’s done at initialization and then never again.