Turn any video or article into your private language classroom
LangKey is the all-in-one language learning browser extension that turns video subtitles, article text, and selected passages into your practice ground. 7 practice modes cover listening, speaking, reading, writing, vocabulary — wrong words auto-enter SRS spaced repetition. Works on YouTube, Bilibili, TED, Netflix, and any web page. Free forever, 10 UI languages.
YouTube
Bilibili
TED
NetflixComing soon
Any Web Page
Three content scenarios, one practice loop
Videos, articles, selection snippets — anywhere you see English, you can turn it into a practice ground.
Learn from Videos
Auto-extract subtitles from YouTube / Bilibili / TED / Netflix. 7 modes (shadowing, dictation, cloze) ready in one click.
Learn from Articles
One click on any BBC / NYT / Medium article to enter full-article learning: original + AI translation, 5 modes reused.
Learn from Snippets
Select any English passage, pop a learning card: deep translation + contextual examples + one-click vocab save, cross-source unified.
4 major video platforms + any web page
Subtitle integration shipped: YouTube / Bilibili / TED. Netflix subtitle integration in progress; Disney+ / Prime Video / Apple TV via generic OCR fallback.
YouTube
Native subtitle extraction, multi-language switching, full compatibility with videos / Shorts / live streams
Supported
Bilibili
WBI interception + multi-scenario adaptation for bangumi / movies / courses
Supported
TED
hls.ted.com direct subtitle push, full talk text + timestamp sync
Supported
Netflix
DFXP / TTML subtitle adaptation + multi-language tracks
Coming soon
Any Web Page
Readability content extraction + generic OCR fallback — articles, PDFs, and videos all learnable
Supported
5 skills in one loop
Listening, speaking, reading, writing, vocabulary — not 5 separate tools, but 5 practice postures on the same content.
Listening
Listening
Listening Mode
TTS sentence-by-sentence / sentence-level pause / complete dictation loop
Speaking
Speaking
Shadowing
Record + speech recognition + AI word-by-word scoring, 0.5x - 2.0x speed adjustable
Reading
Reading
Full-Article Reading
Full-text extraction + AI bilingual comparison + saved vocabulary auto-highlighted in original
Writing
Writing
Input / Dictation
Word-by-word input / AI-generated dictation at your CEFR level / wrong words auto-enter the loop
Vocabulary
Vocabulary
SRS Review
Wrong words auto-enter SM-2 spaced repetition queue, CEFR vocabulary estimation
One sentence, five practice ways
Not 5 tools — 1 sentence, 5 practices. This is the biggest difference from Duolingo or immersive translators.
7+ practice modes, switch on demand
One content pool (video subtitles / article sentences / selection snippets), 7 practice modes switch freely, all results unified and stored.
Input Mode
Word-by-word input of original sentences, strengthens spelling and muscle memory
Option Mode
Shuffle sentence order, understand grammatical structure
Listening Mode
Listen-and-pick / dictation, train real listening ability
Shadowing
Read after original, AI word-by-word pronunciation scoring
Dictation Mode
AI generates dictation at your level, wrong words auto-enter vocabulary
Fill-in Mode
AI-customized cloze exercises, only practice unfamiliar words, skip what you know
AI Conversation
Pick a scenario, AI plays a role, you respond freely
Wrong words auto-enter SRS — LangKey's moat
Unlike immersive translators that focus on "reading," we focus on "practice." All wrong words automatically enter the SM-2 spaced repetition queue and are pushed precisely in the next review.
1
Practice
Any wrong / unfamiliar word from any mode is captured automatically
2
Store
Written to local VocabularyDB with context, source URL, and source platform
3
Review
SM-2 algorithm calculates next review time, push precisely
Free Anki Migration
Support Anki .apkg / CSV / JSON import-export, zero switching cost for existing users
Cross-Source Timeline
See where each word came from — video / article / selection all recorded
CEFR Vocabulary Estimator
Auto-tag learned words A1-C2, see exactly which level you've reached
Learning Center: Your language growth dashboard
Not data dumping — tells you "what to practice today / which words to review / how much progress this week."
Today's Overview
Study time / practice completed / words due for review / streak days
SRS Review Panel
Today's due words + error set, filter by level / source / time
Error Analysis
Spelling / tense / preposition / meaning 4-category error stats, recommend targeted practice
Learning Calendar
GitHub-contribution-style streak visualization, motivation made visible
Open Source · Privacy · Cross-Device · 10 Languages
Privacy First
All learning data stored in local IndexedDB. AI requests only send current sentence/paragraph — no learning records uploaded.
Open & Transparent
Full open-source development, listen to community feedback, public iteration on GitHub
Cross-Device Sync
Progress and vocabulary synced across all browsers via Chrome sync API
Full Keyboard Control
Designed for efficiency enthusiasts, no mouse needed, shortcuts for repeat / skip / lookup
Native Dark Mode
Native dark theme + multi-language UI, easy on the eyes during late-night study
10 UI Languages
Simplified Chinese / Traditional Chinese / English / Japanese / Korean / French / German / Spanish / Russian / Portuguese
Turn your daily browsing into language growth now
Free forever, all Chrome / Edge / Firefox. 3-minute install, start today.