YouTube English Caption Learning Support
A Chrome extension (Manifest V3) that fetches YouTube English captions from timedtext and displays them in a custom overlay. Native captions are hidden in favor of the learning display.
CEFR difficulty coloring, dictionary popups, known-word tracking, level-based word lists, learner level estimation, and caption read-aloud — all designed for vocabulary study while watching videos.
Learning flow (overview)
- Open a YouTube video with English captions.
- The extension overlays captions. Words are color-coded by CEFR band (A1–C1+).
- Hover pauses playback. Click a word for English-English plus Japanese definitions (bundled dictionary first; online API for missing entries).
- Mark words as “known.” Seek to occurrences from the side panel. Estimate your level from the known rate of encountered words.
- Read aloud the on-screen caption independently (adjust speed, voice, and gap between words).
Features
- Pause on caption hover, resume when the pointer leaves
- Word color bands by CEFR (A1–C1+)
- English-English plus Japanese on hover / click (bundled dictionary preferred)
- Phrase and grammar pattern highlights (~1,800 entries)
- Register “known” words and seek to their occurrences
- Estimate learner level from the known rate of encountered words
- Read aloud on-screen captions (speed, voice, word gap)
Scope and notes
Targets YouTube English captions only. Japanese captions, Shorts, and cross-video learning history are out of scope. Word level data comes from CEFR-J / Octanove (CC BY-SA 4.0).
Install by loading an unpacked folder from Chrome’s extensions page, or use the store link once published — this page will be updated. Developer contact: conexsoft@fujigoma.com.
Chrome Web Store
The store listing URL is being prepared. An add button will appear here after publication.
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