I'm aware of the issue that YouTube changed their encoding of the internal video links, basically breaking YTDownloader, should be fixed soon!! UPDATE 16/10/18: Update coming soon!
YTDownloader is a small utility to download YouTube videos directly. The videos are downloaded with the optimal resolution into your documents directory without any hassle (soon to come: conversion into other formats and more)! Also, it's completely portable, no installation required. Small note: even though it's beta it's fully tested, so don't worry about crashes (at least in the full extend I tested, nothing bad happened).
Downloading videos with YTDownloader is easy as one-two-three:
A little bit of waiting and done! You have now the videos on your computer. :)
Requirements: a internet connection, which you probably have. And .NET Framework 4.5 (should be pre-installed on versions of Windows 8 and up)!