I've been using this add-on for a long time..and , to me.. it is the only reliable YouTube video downloader out there..
Kudos on the developers as ..dealing with YouTube's policies and code is not a wall in the park.
Cheers from Portugal !

It works pretty well. Unfortunately, HD (720p) and more require server processing on the part of the addon's developpers (Youtube having split up sound and video), hence a paid license.
NOTE TO THE AUTHOR(s): a feature allowing to download both files anyways would be nice (without the requirement of server processing on your side): I have tools for merging and converting those files myself locally via an Open Source program.

Works well as a low-def in-browser addon, but no addon app for my (ARM Linux) based platform for hi-def videos.

simple, adequate and reliable!

Schön, dass man auch ohne Upgrade (geringe Kosten) MP4 in HD herunterladen kann. Für höherwertige Formate wurde anscheinend eine Fremdfirma beauftragt, wodurch Kosten entstehen.

While I've used this many times, my only complaints have been w/YouTube.

i wish they had webm and wav
but its alright, works as necessary

My go-to downloader. YouTube constantly breaks the code to disable downloaders, but this developer gets replacements up pretty quickly. Not their fault that YouTube constantly breaks the code.