YouTube Thumbnail Language

A Tampermonkey userscript that displays a video’s audio language at the bottom-left of its thumbnail.

Audio metadata: Identifies the language from YouTube’s audio-track information.
Caption fallback: Optionally estimates the language from automatically generated captions, marked with a tiny cc.
Saved settings: Tampermonkey menu commands toggle Original / Default audio preference and enable or disable caption estimates.
Caching: Stores results for up to seven days, with separate caches for each settings combination.
Dynamic loading: Processes nearby thumbnails as you scroll or navigate within YouTube.

Limitations: Language information isn’t available for every video. Original mode falls back to the default track when the original cannot be identified, and YouTube’s default may be a dub. Unavailable metadata shows Unknown; failed requests show Error.