YouTube Shorts and watch pages: only the thumbnail is checked

What is checked on YouTube

• Thumbnails on the home page, search results, the sidebar, Shorts, channel grids, playlists and end screens are checked as images, labelled "video thumbnail".
• Watch pages and embeds. The player is a cross-origin frame and cannot be captured, so the extension derives the video's public thumbnail from its id and checks that instead. The card's muted line says "Checked the video's thumbnail".
• Comments are checked as text, with the writing-pattern analysis and the community cache.
• Shorts are included: the thumbnail of the current Short is checked, with the same limitation.

Video frames are never decoded; nothing in the card claims otherwise. A generated video with a hand-made thumbnail will not be caught; a real video with a generated thumbnail will be flagged for the thumbnail.

Where the circle sits

Bottom-right of the player or thumbnail, 12px in from the edges, one per video. On watch pages the description and comments get their own circles when their text is flagged.

If nothing appears

• The thumbnail must be at least 96 by 96 pixels as rendered; tiny sidebar thumbnails may be skipped.
• Confidence has to reach your preset. Thumbnails are stripped of metadata, so unless a cached classifier result exists they rarely reach 90%. Try Lenient.
• YouTube renders parts of its interface inside open shadow roots, which the extension walks; a YouTube redesign can still break an adapter. If a whole page type stops working, report it.