HappySubs — Dual Subtitles for YouTube

Show two subtitle languages on YouTube at once — native tracks or free Google Translate, with optional AI translation.

Watch YouTube with two subtitle languages at once. 【HOW IT WORKS】 Turn on YouTube's own captions (the CC button), and the extension overlays a second language below them — using the video's native subtitle tracks when available, or free Google Translate otherwise. No account, no setup. 【FEATURES】 • Dual subtitles on any video with captions (including auto-generated ones) • Uses native subtitle tracks first for the best quality • Free Google Translate fallback — works out of the box • Optional high-quality AI translation: Claude, OpenAI, Gemini, or DeepSeek (bring your own API key) • Paid APIs are never called without your explicit confirmation • Adjustable position, font size, color, and background — drag subtitles right on the video • Interface automatically follows your browser language (English / Chinese) 【PRIVACY】 Open source. The extension only reads the current video's captions and sends caption text to the translation service you choose. API keys stay in your browser's synced storage. Nothing is ever sent to the developer. MORE INFO: https://github.com/huanshuowang/youtube-dual-subtitles