Was a great add-on, but has stopped working with Youtube's recent new UI
EDIT: reached out to the dev but got no reply. Changed rating as this currently doesn't work.
EDIT2: working great again with 3.2.0 update :)
EDIT3: stopped working again (oct 2024)

Not working on my tests. Did someone make it work on Firefox 76+?

This software is the only caption download working in youtube so far but the response is very slow. I hope the writer can fix this problem.