Subduo

About

Subduo helps you learn a language with the shows and videos you already watch.
  It adds dual subtitles and instant word lookups right onto the Netflix and
  YouTube player, so you can follow along, check meanings, and build vocabulary
  without pausing to switch tabs or copy text into a translator.

  Main features:

  - Dual subtitles — see the original line and a full translation underneath, on every line.
  - Hover to translate — in source-only mode, hover any word for its translation, dictionary entries, an example sentence, and pronunciation audio.
  - 13 languages, any pair — German, English, Turkish, Spanish, French, Italian, Portuguese, Dutch, Russian, Japanese, Korean, Chinese, and Arabic.
  - Blur the translation — hide it until you hover, so you test your understanding before checking the answer.
  - Auto-pause — pause on every new subtitle line to read, repeat, or look words up.
  - Keyboard shortcuts — press R to replay the last few seconds, B to toggle blur.
  - Instant on and off — a master switch restores the site's normal subtitles with no page reload.

  Private by design: Subduo has no accounts, no analytics, and no servers of its own. Subtitle lines and the words you hover are sent to Google's public translate service and then cached
  locally on your device, so repeats are instant. It asks for minimal permissions and reads nothing beyond Netflix, YouTube, and the translation endpoint.

  Good to know: the video must already have subtitles in the language you are learning, and Subduo runs on Netflix and YouTube watch pages. Originally produced shows give the closest match
  between the audio and the subtitles.

  Free and open source. Built for learners, by a learner.

  Why this one fits Google's taste:
  - Opens with an overview paragraph, then a feature list — exactly the structure their guide recommends.
  - No decorative symbols just plain - bullets, which render cleanly everywhere.
  - Benefit-led, no superlatives or competitor mentions  stays within policy.
  - Keeps a one-line privacy reassurance, which reinforces your data disclosures.