HappySubs — Dual Subtitles & Live Captions

Two subtitle languages at once on YouTube, Vimeo and Bilibili — plus live transcription for videos that have no captions at all.

Two subtitle languages at once on YouTube, Vimeo and Bilibili — and captions for videos that have none. 【HOW IT WORKS】 On YouTube, turn on the player's captions (the CC button) and the extension overlays a second language below them. On Vimeo and Bilibili, it reads the subtitle track directly, so you don't need to turn anything on. It uses the video's own subtitle tracks when they exist, and free Google Translate otherwise. No account, no setup. For videos with no subtitles at all, optional live transcription listens to the audio and writes the captions itself. Recognition runs on your own computer, so the audio never leaves it — and it costs nothing to run. It needs a small local program you install once; everything else works without it. 【FEATURES】 • Works on YouTube, Vimeo and Bilibili • Dual subtitles on any video with captions, auto-generated included • Uses human-authored subtitle tracks first, machine ones as fallback • Free Google Translate by default, optional high-quality AI translation: Claude, OpenAI, Gemini or DeepSeek (bring your own API key) • Paid APIs are never called without your explicit confirmation • Live transcription for videos with no subtitle track (Chinese and English, runs locally) • Adjustable position, font size, color, background and width • Settings page to pin the interface to English or Chinese instead of following your browser 【PRIVACY】 Open source. The extension reads the current video's subtitles and sends that text to the translation service you choose. API keys stay in your browser's storage. With live transcription switched on, audio is sent only to the recogniser on your own machine over a loopback connection — never uploaded, never sent to the developer. It never uses your microphone. MORE INFO: https://huanshuowang.com/happysubs/