Kodi Community Forum

Hi:
This feature does not run. Any videos watched (e.g. from YouTube) are not hidden from long time, probably since 17.2 version.
Marek

The watched status of 3rd party streaming add-ons would be a function of that add-on and its support would be in either the associated forum or contact the author. You might want to investigate the add-on 'Last Played'.