VocabRadar od VocabRadar.com

VocabRadar — discover your own new words in the content you were going to watch
or read anyway.

[Learn words from videos]
· On Bilibili / YouTube video pages, a side panel shows the subtitle list with
your new words highlighted, plus a word list for the video.
· Subtitles can be overlaid on the video with highlights and inline translations.
· Notes switch between compact (word + gloss) and detailed (headword, full
senses, word-list tags, frequency band).
· Click a subtitle timestamp to jump straight to that line.
· One click copies the annotated subtitles to the comment box, or exports your
word list.

[Learn words from the web]
· On any web page: new words highlighted in the body text, side annotations,
hover definitions, right-click lookup.
· The in-page sidebar collects the page's new words with their sentences.

[Learn even without subtitles]
· Built-in local speech recognition (Whisper) turns subtitle-less videos,
recordings, or uploaded audio/video into learnable text.
· OCR reads text in the current video frame (burned-in subtitles, slides).

[AI chat]
· A built-in chat window works with free built-in models, or fill in your own
OpenAI / Anthropic-compatible key.

[Why "your own new words"]
· Words are flagged by frequency threshold: common words stay quiet, rare words
get flagged. You tune the threshold.
· Word-frequency and word-list data ship inside the extension — lookups need no
account and never upload your browsing history.

No sign-up, no account. Install and learn.