According to AlphaMoat, as of 2026-09, the Chrome extension LessonSide has 43 users (+104.8% MoM), rated 5 (4 reviews) — ranked #5,754 of 9,324 AI browser extensions, and #433 of 676 in Education & Research.
What is LessonSide
AI tutor for YouTube lessons: auto study notes, quizzes to test yourself, and screenshot Q&A on the exact frame you're stuck on. LessonSide — Your AI tutor for YouTube lessons
Make every YouTube lesson count. Get auto study notes, and quiz yourself, ask about anything on screen — all while you watch.
🎯 What it does
Auto notes for every lesson. It turns every lesson into organized key points — so you don't have to write anything down.
A quick quiz on what you learned. It verifies you actually understood the lesson — not just watched it. Interactive questions, instant feedback, and a way to spot the gaps.
Something on screen isn't clicking? Screenshot it and ask — understand it without leaving the video. Box a formula, diagram, or line of code and get a clear explanation right where you're watching.
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Ask anything, anytime. Ask about the lesson as you watch and get answers grounded in the video — like having a tutor sitting right next to you.
Works on YouTube and Bilibili video pages.
📖 How to use
Install the extension and open any YouTube lesson. Click the elephant icon at the top-right of your browser to open the side panel. The assistant activates automatically — start asking, or use Notes and Quiz. For the best experience, click Theater Mode at the bottom-right of the player.
💡 Who it's for
Anyone teaching themselves programming, math, AI, or deep learning from YouTube lectures Students studying for exams with online courses Learners following courses from Andrew Ng, 3Blue1Brown, MIT OpenCourseWare, and more Anyone who wants to make every YouTube lesson count
✨ Why LessonSide
Screenshot-to-ask is our standout feature — box a formula, diagram, or line of code and get it explained without leaving the video.
Notes, chat, and quiz in one place — understand, summarize, and verify without switching tools.
Full math rendering (KaTeX) — formulas and STEM content display perfectly.
Built for focus — each video gets its own notes, chat, and quiz, so your study stays organized lesson by lesson.
🔒 Privacy
We only access the video page you're actively watching — we don't track your general browsing.
To provide the tutoring features, we process your email (for login), the video's subtitles, your chat messages, and any screenshots you capture. This data is stored securely and never used for advertising.
Full details — including Google sign-in and third-party AI processing — are in our privacy policy.
Privacy policy: https://lessonside.com/privacy/
📬 Contact: [email protected]
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+ CompareData month: 2026-09 · User counts and ratings come from public Chrome Web Store data, aggregated monthly. See methodology.