DualTrans - Bilingual YouTube Subtitles

AI-powered bilingual subtitles for YouTube with customizable styles, dual translation display, and smart synchronization.

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Inspiration

Language barriers shouldn't hold anyone back from accessing global knowledge, entertainment, and tutorials on YouTube. Standard auto-generated captions often lack dual-language contexts, nuance, or formatting flexibility. DualTrans was built to provide learners and global viewers with an effortless, immersive bilingual viewing experience.

What it does

DualTrans is a lightweight, high-performance browser extension that displays bilingual subtitles simultaneously on YouTube:

  • Dual-Language Subtitles: View both the original and translated subtitles at the same time.
  • AI-Powered Translations: Leverages cutting-edge translation models for natural phrasing and cultural accuracy.
  • Customizable Styling: Adjust font sizes, subtitle position, colors, and backgrounds for optimal readability.
  • Bilingual Transcript & Download: Search, review, and export timestamped video transcripts for efficient study.
  • Broad Language Support: Translates between English, Spanish, Chinese, Japanese, Korean, French, German, and 50+ languages.

How we built it

  • Core Extension: Built using TypeScript, modern Chrome Extension Manifest V3, Webpack, and Tailwind CSS.
  • Landing & Platform: Next.js 14 App Router, TypeScript, Tailwind CSS, and optimized internationalization (i18n).
  • Subtitles Engine: Intercepts and parses YouTube caption streams, synchronizing translated cue points in real time without lag.

Challenges we ran into

Handling dynamic DOM updates in YouTube's modern Single Page Application architecture while maintaining smooth frame rates and non-intrusive subtitle rendering across full-screen and theater modes was an exciting technical challenge.

Accomplishments that we're proud of

  • Seamless synchronization with YouTube's native video controls.
  • Zero-latency subtitle rendering with customizable UI overlays.
  • Loved by international students and bilingual video consumers worldwide.

What's next for DualTrans

  • Extending support to additional video streaming platforms (Coursera, Udemy, Netflix).
  • Offline AI subtitle caching and vocabulary flashcard integration.

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