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. Supports 10 UI languages.

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YouTube

Bilibili

TED

NetflixComing soon

Any Web Page

LangKey HD Product Demo

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.

探索模式

Learn from Articles

One click on any BBC / NYT / Medium article to enter full-article learning: original + AI translation, 5 modes reused.

探索模式

Learn from Snippets

Select any English passage, pop a learning card: deep translation + contextual examples + one-click vocab save, cross-source unified.

探索模式

SCENARIO PREVIEW // Learn from Videos

YouTube 双语动态字幕

"Learning a language isn't about memorizing rules, it's about immersive practice."

“学习语言不是死记硬背规则，而是沉浸式的实践练习。”

影子跟读逐句听写错词入库

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

Supported

Native subtitle extraction, multi-language switching, full compatibility with videos / Shorts / live streams

Bilibili

Supported

WBI interception + multi-scenario adaptation for bangumi / movies / courses

TED

Supported

hls.ted.com direct subtitle push, full talk text + timestamp sync

Netflix

Coming soon

DFXP / TTML subtitle adaptation + multi-language tracks

Any Web Page

Supported

Readability content extraction + generic OCR fallback — articles, PDFs, and videos all learnable

5 skills in one loop

Listening, speaking, reading, writing, vocabulary — not 5 separate tools, but 5 practice postures on the same content.

Listening

Listening Mode

TTS sentence-by-sentence / sentence-level pause / complete dictation loop

Speaking

Shadowing

Record + speech recognition + AI word-by-word scoring, 0.5x - 2.0x speed adjustable

Reading

Full-Article Reading

Full-text extraction + AI bilingual comparison + saved vocabulary auto-highlighted in original

Writing

Input / Dictation

Word-by-word input / AI-generated dictation at your CEFR level / wrong words auto-enter the loop

Vocabulary

SRS Review

Wrong words auto-enter SM-2 spaced repetition queue, CEFR vocabulary estimation

核心差异化

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.

Practice

Any wrong / unfamiliar word from any mode is captured automatically

Store

Written to local VocabularyDB with context, source URL, and source platform

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

Supported on Chrome, Edge, and Firefox. 3-minute install, start today.