Subz — Learn English from Subtitles

Master English while watching YouTube. Smart subtitle vocabulary highlighting, instant definitions, and your personal notebook.

Turn every YouTube video into an effortless English masterclass. Subz is a lightweight extension that intelligently underlines uncommon and advanced English vocabulary in subtitles, displays instant context-aware definitions, and helps you build a personal vocabulary notebook—without ever breaking your watching flow. Whether you are watching tech reviews, TED Talks, podcasts, interviews, or documentaries, Subz helps you expand your vocabulary naturally in context. ─────────────────────────────── ✨ KEY FEATURES ─────────────────────────────── 🎯 Smart Subtitle Highlighting • Automatically evaluates video captions against an Oxford 3000 / CEFR common-word database. • Underlines uncommon and advanced words (e.g., "dissect", "nuance", "pragmatic", "semantic") in elegant Subz Amber. • Common conversational words and brand names are never falsely highlighted. ⚡ 0ms Instant Definition Engine • Speculative Prefetching: Pre-fetches word definitions in the background while you read captions. • Built-in Offline Core Dictionary: High-yield B2/C1/C2 words resolve instantly offline with beginner-friendly explanations. • Intelligent Lemmatizer: Seamlessly resolves plurals, past tense, and inflected forms ("nuances" → "nuance"). 🃏 Minimalist Word Card Popover • Apple-grade minimalism (distraction-free typography). • Crisp audio pronunciation with 1.0x and 0.75x slow speeds. • "IN THIS SCENE" quote box displays the exact dialogue sentence where the word appeared. • Native YouTube player integration: Click "Resume ▶" or "↺ Replay 5s" without player desync. 📓 Personal Vocabulary Notebook & Habit Tracker • Save any word to your personal notebook with one click. • Daily Habit Goal: Stay motivated with a daily progress bar and streak counter. • 1-Click Export: Download your saved words anytime as a clean .txt study sheet. • Quick Search: Look up any word inside the popup or via right-click. ─────────────────────────────── 🔒 PRIVACY & SECURITY FIRST ─────────────────────────────── • 100% Client-Side: Runs entirely in your browser. • Zero Data Tracking: We never collect passwords, browsing history, or personal data. • Local Storage: Your saved words, streak, and preferences remain strictly on your device. • Ad-Free & Lightweight: No tracking scripts, no third-party ads. ─────────────────────────────── 💡 HOW TO USE ─────────────────────────────── 1. Install Subz and pin it to your Chrome toolbar. 2. Open any English YouTube video with subtitles enabled (press "C" on YouTube). 3. Uncommon words are gently underlined. 4. Click any underlined word to open the Word Card. 5. Listen to the pronunciation, save the word to your notebook, and hit Resume!