How NoteSynth Works: A Behind-the-Scenes Look
Ever wondered how NoteSynth transforms video lectures into perfectly formatted study notes? In this post, we'll walk you through the entire process—from entering your Udemy cookie to downloading your organized notes.
The 5-Step Process
Authentication
When you paste your Udemy cookie, NoteSynth uses it to access the Udemy API on your behalf. This is the same cookie your browser uses when you watch courses—no password required.
📝 Note: Your cookie is stored only in your browser's local storage. It never leaves your device except to make requests directly to Udemy.
Course Discovery
Once authenticated, NoteSynth fetches your enrolled courses from Udemy's API, including:
Lecture Selection
You choose which lectures you want notes for. Select individual lectures, entire chapters, or choose "Select All" for the complete course.
💡 Tip: For large courses, we recommend generating notes chapter-by-chapter to avoid timeouts.
Configure Settings (Optional)
Tailor the output to your liking by visiting the Settings page:
Custom Prompt
Edit the AI instructions to change formatting, add sections, or adjust note style.
Output Format
Choose between individual files per chapter or combined files with Table of Contents.
Caption Extraction & AI Processing
This is where the magic happens! For each selected lecture:
Caption Fetch - NoteSynth retrieves the English captions from Udemy
VTT Parsing - The raw caption file is cleaned up, removing timestamps
AI Enhancement - The transcript is sent to Groq or Gemini
## Lecture Title
Key concept explanation with proper formatting...
- 📌 **Example:** Real-world application
- 💡 **Tip:** Best practice suggestion
- ⚠️ **Warning:** Common mistake to avoid
```python
def example():
return "formatted nicely"
```ZIP Generation & Download
After all lectures are processed:
Technical Architecture
┌─────────────┐ ┌─────────────┐ ┌─────────────┐
│ Browser │────▶│ Next.js │────▶│ Udemy API │
│ (React) │ │ API Routes │ │ │
└─────────────┘ └──────┬──────┘ └─────────────┘
│
▼
┌─────────────┐
│ AI Service │
│ (Groq/Gemini)│
└─────────────┘Key Technologies:
Performance Optimizations
⚡ Parallel Processing
Instead of processing lectures one-by-one, we use concurrent requests with intelligent rate limiting:
10 lectures: ~20 seconds (vs 50+ seconds)
🔄 Smart Retry Logic
Rate limits happen. NoteSynth automatically:
- Detects 429 Too Many Requests errors
- Waits with exponential backoff
- Falls back to alternate AI provider
Privacy & Security
We take your privacy seriously:
| Data | Stored Where | Duration |
|---|---|---|
| Udemy Cookie | Browser localStorage | Until you clear it |
| Course Data | Browser memory | Current session only |
| Generated Notes | Your downloads folder | You control it |
We never store: Your cookies on our servers, your course content, your generated notes, or any personal information.
Ready to try it?
NoteSynth is 100% open source under the MIT license.