youtube-dl is not working

Same question was asked on unix.stackexchange.com.

Youtube changed something to make it incompatible with youtube-dl, it's been fixed in the latest version. Use the following to update youtube-dl until the package system gets the updated version:

sudo youtube-dl -U

Update

As noted by sup in the comments youtube-dl is patched in Ubuntu to disable the --update option because of security concerns (the bugreport is here). It is also argued in the bugreport that youtube-dl is a moving target, so the version in the repositories is often out of date. This makes easy upgrade a necessity.

Easy upgrade is still possible with e.g. pip. Install like this (you may want to uninstall old versions of youtube-dl first):

sudo pip install youtube_dl

Upgrading can now be done with:

sudo pip install --upgrade youtube_dl

As documented on the youtube-dl download page. Note that similar security concerns are attached to this method as well.

For me the following lines worked:

sudo apt-get remove -y youtube-dl
wget -O - https://yt-dl.org/latest/youtube-dl | sudo tee /usr/local/bin/youtube-dl > /dev/null
sudo chmod a+x /usr/local/bin/youtube-dl
hash -r