I'm speaking of sheer inexperience but are safe sources of royalty free material for commercial purposes with zero risk of illegitimate claims or any hassle by the authors/owners/uploaders of that material if they see their material being used commercially in a video reaching ...say... 1.5M views and they decide to actually make illegitimate claims? Is that even possible for them - given the source and their policies? I have a certain amount of unease when it comes to downloading royalty-free material mostly stemming from inexperience but there are people who would go far lengths to try getting something more in return after seeing their material being used in a video reaching a huge amount of views... Is there some kind of a preventive measure one can take to later prove that at the time you utilized the material it was indeed free for commercial purposes? I heard of a lot of examples where honest folks' YouTube channels got handicapped for weeks on end for every kind of preposterous claims and I don't want to get burned. Where should I turn to - to be sure of no hassle coming down the line?