Unlisted videos rely entirely on "security through obscurity." If you do not have the link, the video is practically invisible. Browser extensions do not hack YouTube's servers to change these permissions; instead, they act as aggregators, scrapers, and historical databases that collect links that were once made public elsewhere. The Reality of "Show Unlisted Videos" Extensions
On YouTube, a video's privacy can be set to one of three options: show unlisted videos youtube extension
If you have the URL (e.g., youtube.com/watch?v=ABC123 ), you can watch an unlisted video. If you lose that URL, you cannot stumble upon it via YouTube search. Unlisted videos rely entirely on "security through obscurity
Go to the Firefox Add-ons or Chrome Web Store and search for "Show Unlisted Videos". they act as aggregators