Windows Freeware Guide: Firefox Add-On - Mark Watched YouTube Video FREE on Windows 11

To be more specific, this FREE add-on marks the thumbnails of the videos when you click video links to open them.

The test steps - Watchmarker for Youtube 4.2.1
OS: Windows 11 Home
Install: https://addons.mozilla.org/en-US/firefox/addon/watchmarker-for-youtube/

1. Installing: open Firefox, go to a link above, click 'Add to Firefox'.

The message shows.

Click 'Add'. Icon of this add-on shows at the toolbar.

2. I went to Youtube.com, searched 'pole saw', opened a video in the new tab, the video wasn't played because I didn't click 'Play', the thumbnail of that video was already marked.

In the channel, its thumbnail was marked too.

I reloaded the landing page of clicking the search result, there was no mark or tag indicating the video was watched.

I clicked the icon of this add-on at the toolbar, scrolled to the bottom, the search section showed. (see the picture below)

You can click the title of the video to watch it.

3. I removed the first item by clicking the 'trash can' icon.

The message showed.

I clicked 'Close'. In the search section, that item was removed.

I reloaded the search result page, there was no mark on the video. Then the channel page was reloaded, I got the same result.

I thought the message 'error deleting video' (see the picture above) indicating that this add-on couldn't find the video in the youtube history so nothing was removed.

I have used this add-on for a long time, I remembered that I tried to delete marks of specific videos, but I couldn't find the way until I installed the latest version in order to write this article, I'm glad this add-on lets me do what I want.

4. I scrolled up to the database section to back it up.