Cortex is the open-source, local-first alternative to Google NotebookLM. Same idea — turn your sources into study material and chat with citations — but your data lives on your machine, it runs offline, you bring your own AI key, and it never silently rewrites your notes.
An honest look. NotebookLM is polished and zero-setup; Cortex trades a little setup for ownership, privacy and a lot more study tooling.
| Feature | Cortex | NotebookLM |
|---|---|---|
| Open source | ✓ Apache-2.0 | ✗ proprietary |
| Where your data lives | On your device (local SQLite) | Google's cloud |
| Works offline | ✓ with local Ollama | ✗ cloud-only |
| AI provider | Bring your own — OpenRouter, Gemini, Claude, OpenAI or local Ollama | Google Gemini only |
| Living cheatsheets | ✓ approve-to-merge diffs — never silently drops a point | ✗ |
| Flashcards + spaced repetition | ✓ FSRS scheduler | ✗ |
| Quizzes & exams | ✓ | ✗ |
| Lecture recording + transcription | ✓ in-app, Whisper | upload audio only |
| Audio overviews | ✓ two-host | ✓ (a NotebookLM strength) |
| Citations to source | ✓ page / timestamp | ✓ |
| Themes | ✓ 10 built-in, syncs with Omarchy | ✗ |
| Platforms | Linux, macOS, Windows + iOS | Web only |
| Self-host / homelab | ✓ sync & AI on your own box | ✗ |
| Price | Free & source-available (you pay only your AI usage) | Free with a Google account |
Comparison reflects publicly documented features as of 2026. NotebookLM is a trademark of Google; Cortex is an independent open-source project.
Cortex stores everything in a local database on your own device. The only thing that ever leaves is the context you send to the AI provider you chose — and with local Ollama, nothing leaves at all. No accounts, no servers of ours, no lock-in.
When a new source updates a cheatsheet, Cortex shows you a diff and waits. NotebookLM regenerates; Cortex never silently drops the point you needed.
Use OpenRouter, Gemini, Claude, OpenAI — or run fully offline with Ollama. You control the model and the cost, not a single vendor.
Beyond chat and audio: flashcards with spaced repetition, quizzes, exams, and a Subjects → Topics → Sources structure built for a real course load.
Native on Linux, macOS and Windows (plus iOS), keyboard-first, 10 themes, and an optional homelab mode that runs transcription, search and models on your own hardware.
No tool wins for everyone — here's where Google's is the smarter choice:
If instead you care about owning your data, working offline, open source, and a full study toolkit — that's exactly what Cortex is for.
Free, source-available, and yours to run anywhere. Bring your own key or go fully offline.