How to keep track of files?

Its pretty much the title I'm just genuinely wondering how you guys are keeping track of all of your legally sourced files. I'm pretty much just relying on a spreadsheet but is that really the best way? Especially for the less technically inclined individuals such as myself

Edit: I apologize thought it was obvious but looking back I could've been more specific. I was referring to movies, TV shows, YouTube videos, books, audiobooks, etc. I haven't taken the leap to self host anything yet just growing my library for now on a couple of encrypted drives until the time comes. You don't really need to provide tailored answers towards my situation I just want to know what's out there in terms of keeping track of stuff. Thank you in advance since this account is a burner and I check it like once a day

Edit #2: appreciate all of your feedback. Seems the majority rely on jellyfin and other software to automatically check what you have stored which I didn't even know it could do that's interesting.