For those wondering why the Ext won't merge. It is reported that large-size video is very likely to be interrupted while downloading, which will fail in starting any follow-up process (including merging) even such download can be continued to finish. So it is suggested to have another ffmpge-based media converter Ext and do the merging manually, which maybe the season those function in early version be cancelled.

the only application that allows me to download private videos from you tube

it works

It is a MUST add-on for FF w/YouTube

it's work! Thanks

Downloads in VP9 where possible in all qualities. Unfortunately you sometimes have to assemble the separated video and audio file with ffmpeg through terminal.

this is so easy to use! thank you!