Dual Subtitles for Netflix & YouTube — Butterfluent

Learn German (or French, Spanish, Italian, Portuguese, Japanese, Korean, Chinese, or Russian) while watching the videos you already enjoy. Butterfluent adds a real-time translated subtitle track alongside the original audio, synced to the video. Works on supported video platforms. Click any word in the subtitle for an instant AI-powered lookup, save it to your flashcard deck, and review it later with spaced repetition — all without leaving the video player. Supported learning languages: German, French, Spanish, Italian, Portuguese, Japanese, Korean, Chinese, and Russian. Dual subtitles Watch with the original dialogue and your target language displayed side by side, perfectly in sync with the video. Works with YouTube auto-generated captions, Netflix subtitle tracks, and every other supported platform. AI word lookup Click any word to see its CEFR vocabulary level (A1 through B2), base form, part of speech, translation in context, and up to three example sentences drawn from the current video. Request a grammar explanation with a second tap. CEFR word highlighting Words in the transcript panel are colour-coded by difficulty so you can see at a glance how demanding a video is — green for A1, blue for A2, orange for B1, red for B2. Flashcard decks and spaced repetition review Save words directly from subtitles and they land in a flashcard deck on your Butterfluent account. The built-in SM-2 spaced repetition algorithm schedules each word for review at the right moment so nothing slips through. Comprehension mode Hide the translated subtitle by default and tap to reveal it. A natural way to test yourself before checking the answer. Smart pause Optionally pause the video automatically whenever a B1 or B2 difficulty word appears, so you have time to read and understand without missing the next line. Subtitle sync nudge Shift the subtitle timing forward or backward in 250 ms steps directly from the settings panel to fix tracks that are slightly out of sync. Session tools Save the current subtitle line as a context sentence with the B key. Export your session word list as a CSV spreadsheet. View the live transcript with CEFR-highlighted words in the study panel. Cycle through target languages without leaving the video. Playback overlay A minimal always-visible overlay shows your current playback speed and gives you one-click access to subtitle toggle, auto-pause, language switch, and sentence save — no need to open any panel. Keyboard shortcuts H — Toggle subtitles on/off P — Toggle auto-pause B — Save current sentence Works with your Butterfluent account Sign in to sync saved vocabulary, review progress, and plan access across devices. Review due cards on the Butterfluent website or continue straight from the extension popup. How to get started 1. Install Butterfluent 2. Open a YouTube video or Netflix show with subtitles in your target language 3. Click the Butterfluent icon and choose your target language 4. Dual subtitles appear — click any word to look it up and save it Free plan includes word lookup, CEFR highlighting, and flashcard creation. Pro plan removes limits on subtitle translations, AI lookups, and flashcard generations. Privacy Butterfluent reads subtitle text on supported video pages to render overlays and study controls. Settings and sign-in state are stored locally in Chrome extension storage. Translation and word-lookup requests send the selected word and its subtitle context to Butterfluent servers. Butterfluent does not sell your data and does not use your browsing activity for advertising. Learn more: https://butterfluentgerman.com Privacy policy: https://butterfluentgerman.com/privacy