HappySubs — Dual Subtitles & Live Captions for YouTube™, Vimeo & Bilibili

Dual subtitles on YouTube, Vimeo and Bilibili. Translate the captions, read both languages as one line, export them as .srt.

Dual subtitles on YouTube, Vimeo and Bilibili — two languages on one line, and captions for videos that have none. 【HOW IT WORKS】 On YouTube, turn on the player's captions (the CC button) and HappySubs translates them, showing the original and the translation together as a single subtitle. On Vimeo and Bilibili it reads the subtitle track directly, so there is nothing to switch on. It uses the video's own subtitles when they exist and free Google Translate otherwise. No account, no sign-in, 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, including Vimeo players embedded in other sites • Both languages as one subtitle: they appear and change together, once per sentence • Dual subtitles on any video with captions, auto-generated included — read as whole sentences, not words scrolling in • Human-authored subtitle tracks preferred, machine ones as fallback • Free Google Translate by default; optional AI translation with Claude, OpenAI, Gemini or DeepSeek using your own API key — and you choose the model • Paid APIs are never called without your explicit confirmation • Live transcription for videos with no subtitle track (Chinese and English, runs locally) • Translation-only mode: read just the translation with the player's captions closed • Download any video's subtitles as .srt — both languages, the original alone, or the translation alone • One shortcut turns the second language on and off without opening the popup: ⌘⇧S, or Alt+Shift+S on Windows and Linux • Style the original and the translation separately, or lock them together; position, size, colour, background and width are all adjustable, and you can drag the subtitle itself, fullscreen included • The subtitle moves clear of the player's controls when you pause • 100+ target languages • Interface in English or Chinese, following your browser or pinned to one 【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 goes only to the recogniser on your own machine over a loopback connection — never uploaded, never sent to the developer. It never uses your microphone, and there is no tracking or analytics of any kind. MORE INFO: https://huanshuowang.com/happysubs/