TwoSub

About

TwoSub adds bilingual (English + Traditional Chinese) dual subtitles to Netflix, YouTube, and HBO Max, so you can enjoy a show and
  learn a language at the same time.

  KEY FEATURES
  • Dual subtitles — the original English and a Chinese line together, synced to playback.
  • Instant word lookup — pause and click any English word for its meaning, phonetics, definitions, and British pronunciation audio.
  • Works on Netflix, YouTube, and HBO Max.
  • No setup for most videos — uses the platform's own subtitle tracks when available, and YouTube's free auto-translate for the
  second language.
  • Per-platform appearance — font, size, position, background, and color, adjustable for each platform independently.
  • In-player toggle — switch the dual subtitles on/off right from the video's control bar.
  • British female pronunciation for word audio.

 HOW IT WORKS
  TwoSub reads the subtitle data the player already loads and renders a clean overlay. For AI translation and contextual word
  meanings, add your own free Google Gemini API key in the options page (optional — core dual-subtitle features work without it).

  PRIVACY
  TwoSub has no server of its own and does not track you. Your settings and API key stay in your browser. Subtitle text and looked-up
  words are sent only to Google Gemini (with your own key) and the Free Dictionary API, only when needed.
  Full policy: https://github.com/vi000246/twosub/blob/main/PRIVACY.md